Beta-adrenoceptor responses to inhaled salbutamol in normal subjects

Quantitative Assessment of the Airway Response to Bronchial Tests Based on a Spirometric Curve Shift

OBJECTIVE

Although spirometry is the most common pulmonary function test, there is no method to quantitatively infer about airway resistance or other properties from the flow-volume curves. Recently, an identifiable inverse model for forced expiration was proposed, as well as the idea to deduce changes in airway resistances and compliances from spirometric curve evolution. The aim of this work was to combine the above advances in a method for assessing the airway response to bronchial tests from a spirometric curve shift.

METHODS

The approach is based on the differential measurement of the degree, site of maximal effect and width of changes, further recalculated into relative changes in the distribution of airway resistances (δR_g) and compliances (δC_g) along the bronchial tree. To this end, appropriate models were identified using the pre- and post-test spirometry data. The accuracy was validated using sets of data simulated by the anatomy and physiology based models. Finally, the method was used to analyze the bronchodilation tests of three asthmatic subjects.

RESULTS

The expected errors in assessing the degree, site and width of changes in the zone of conducting airways were 6.3%, 2.4 generations and 22%, respectively, and for δR_g and δC_g were 5-10% and 13-16%, respectively. The analyses of clinical data indicated a significant reduction in resistances and an increase in compliances of airway generations 8-12, consistent with clinical knowledge.

CONCLUSION

An unprecedented method to plausibly transforming the spirometry data into the site and degree of changes in airway properties has been proposed.

SIGNIFICANCE

The method can be used to deduce about the effects of bronchial tests, as well as to monitor changes in the airways between visits or to investigate how inhaled pharmaceuticals affect the bronchi.

Repeat dosing of albuterol via metered-dose inhaler in infants with acute obstructive airway disease: a randomized controlled safety trial

BACKGROUND

Airway obstruction and bronchial hyperactivity often times lead to emergency department visits in infants. Inhaled short-acting beta2-agonist bronchodilators have traditionally been dispensed to young children via nebulizers in the emergency department. Delivery of bronchodilators via metered-dose inhalers (MDIs) in conjunction with holding chambers (spacers) has been shown to be effective.

STUDY OBJECTIVE

: Safety and efficacy evaluations of albuterol sulfate hydrofluoroalkane (HFA) inhalation aerosol in children younger than 2 years with acute wheezing caused by obstructive airway disease.

METHODS

A randomized, double-blind, parallel group, multicenter study of albuterol HFA 180 microg (n = 43) or 360 microg (n = 44) via an MDI with a valved holding chamber and face mask in an urgent-care setting. Assessments included adverse events, signs of adrenergic stimulation, electrocardiograms, and blood glucose and potassium levels. Efficacy parameters included additional albuterol use and Modified Tal Asthma Symptoms Score ([MTASS] reduction in MTASS representing improvement).

RESULTS

Overall, adverse events occurred in 4 (9%) and 3 (7%) subjects in the 180-microg and 360-microg groups, respectively. Drug-related tachycardia (360 microg) and ventricular extrasystoles (180 microg) were reported in 1 patient each. Three additional instances of single ventricular ectopy were identified from Holter monitoring. No hypokalemia or drug-related QT or QTc prolongation was seen; glucose values and adrenergic stimulation did not significantly differ between treatment groups. In the 180-microg and 360-microg groups, mean change from baseline in MTASS during the treatment period was -2.8 (-49.8%) and -2.9 (-48.4%), and rescue albuterol use occurred in 4 (9%) and 3 (7%) subjects, respectively.

CONCLUSIONS

Cumulative dosing with albuterol HFA 180 microg or 360 microg via MDI-spacer and face mask in children younger than 2 years did not result in any significant safety issues and improved MTASS by at least 48%.

Safety of daily albuterol in infants with a history of bronchospasm: a multi-center placebo controlled trial

Introduction:

Inhaled short-acting bronchodilators are recommended for the quick relief of bronchospasm symptoms in children including those less than five years of age. However, limited safety data is available in this young population.

Methods:

Safety data were analyzed from a randomized, double-blind, parallel group, placebo-controlled multicenter, study evaluating albuterol HFA 90µg or 180µg versus placebo three times a day for 4 weeks using a valved holding chamber, Aerochamber Plus and facemask in children birth ≤24 months old with a history of bronchospasm.

Results:

The overall incidence of adverse events (AE) during treatment was: albuterol 90µg (59%), albuterol 180µg (76%) and placebo (71%). The most frequently reported AEs were pyrexia in 7 (24%), 2 (7%), and 3 (11%) subjects in the albuterol 180µg, albuterol 90µg, and placebo groups, respectively. Upper respiratory tract infection (URTI) occurred in 5 (17%) and 3 (11%) subjects in the albuterol 180µg and placebo groups, respectively. Sinus tachycardia occurred in 5 (17%), 2 (7%) and 2 (7%) subjects receiving albuterol 180µg, albuterol 90µg and placebo, respectively. One subject in each of the albuterol treatment groups experienced drug related agitation and/or restlessness or mild sinus arrhythmia. No drug-related QT prolongation or abnormal serum potassium and glucose levels were reported in the albuterol treatment groups.

Conclusion:

This study provides additional albuterol HFA safety information for the treatment of children aged birth ≤24 months with a history of bronchospasm.

Inhaled beta2-adrenoceptor agonists: cardiovascular safety in patients with obstructive lung disease

Although large surveys have documented the favourable safety profile of beta(2)-adrenoceptor agonists (beta(2)-agonists) and, above all, that of the long-acting agents, the presence in the literature of reports of adverse cardiovascular events in patients with obstructive airway disease must induce physicians to consider this eventuality. The coexistence of beta(1)- and beta(2)-adrenoceptors in the heart clearly indicates that beta(2)-agonists do have some effect on the heart, even when they are highly selective. It should also be taken into account that the beta(2)-agonists utilised in clinical practice have differing selectivities and potencies. beta(2)-agonist use has, in effect, been associated with an increased risk of myocardial infarction, congestive heart failure, cardiac arrest and sudden cardiac death. Moreover, patients who have either asthma or chronic obstructive pulmonary disease may be at increased risk of cardiovascular complications because these diseases amplify the impact of these agents on the heart and, unfortunately, are a confounding factor when the impact of beta(2)-agonists on the heart is evaluated. Whatever the case may be, this effect is of particular concern for those patients with underlying cardiac conditions. Therefore, beta(2)-agonists must always be used with caution in patients with cardiopathies because these agents may precipitate the concomitant cardiac disease.

Bronchoprotection with formoterol via dry powder and metered-dose inhalers in patients with asthma

BACKGROUND

Determination of device comparability for new inhaled medications is essential.

OBJECTIVE

To evaluate the methacholine bronchoprotection afforded by formoterol, 12 microg, delivered via Clickhaler and Aerolizer dry powder inhalers and a pressurized metered-dose inhaler (pMDI) in mild-to-moderate asthmatic patients.

METHODS

Two separate randomized, double-blind, double-dummy, crossover studies were performed. Peak bronchoprotection (30 minutes) was measured after administration of a single dose in a placebo-controlled study (n = 16). First-dose (8 hours) and trough (12 hours) protection were evaluated after 2 weeks (n = 28). Doubling dilution differences (DDD) in the methacholine provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20% from baseline were compared, with equivalence defined if the 95% confidence interval was within the predefined equivalence limits of +/- 1.5 DDD (peak) and +/- 1.0 DDD (trough).

RESULTS

For peak single-dose effects, DDD (95% confidence interval) data showed significant protection vs placebo for all devices but no significant differences among active inhalers. For trough first-dose effects, there was significant protection vs baseline for all devices and equivalence for Clickhaler vs Aerolizer (-0.41; -0.85 to 0.04) and Aerolizer vs pMDI (-0.27; -0.66 to 0.13) but not for Clickhaler vs pMDI (-0.68; -1.12 to -0.23). For trough effects after 2 weeks, there was significant residual protection from baseline and equivalence for Clickhaler vs Aerolizer (-0.32; -0.94 to 0.30), Clickhaler vs pMDI (0.34; -0.96 to 0.27), and Aerolizer vs pMDI (-0.02; -0.57 to 0.52).

CONCLUSIONS

Formoterol delivered by 3 different inhalers exhibited a significant degree of peak and trough bronchoprotection after single and repeated dosing, with most comparisons being within predefined equivalence limits.

Effect of nebulized albuterol on blood glucose in patients with diabetes mellitus with and without cystic fibrosis

Over 90% of cystic fibrosis (CF) patients are treated with bronchodilators, and 6% have diabetes. Some with asthma also have diabetes, and most are treated with bronchodilators. Systemic administration of adrenergic agents can cause increases in blood glucose, but the effect of inhaled agents is unclear. A double-blind study was performed on 10 patients with type 1 diabetes mellitus (DM) without CF (3 male, 7 female, mean age 25.5 years) and 9 patients with insulin-dependent CF-related diabetes (CFRD) (8 male, 1 female, mean age 21.9 years). On 2 separate days before 9 AM fasting and the morning dose of insulin, 2.5 mg of albuterol or nebulized placebo were given. Blood glucose was measured by finger stick with a glucose reflectance meter before and 15, 30, 45, and 60 min after treatment. No significant changes from baseline or differences between placebo and albuterol occurred in either group. The mean maximum increase from baseline in DM was 20 mg/dl on placebo, and 38 mg/dl on albuterol; in the CFRD, the respective changes were 7 and 7 mg/dl. Two DM patients had a > 50 mg/dl increase on albuterol vs. placebo; no CFRD patients had differences of such magnitude. DM patients had greater increases from baseline than CFRD patients on placebo and albuterol. Differences reached statistical significance at 30 and 45 min on placebo, and 45 min on albuterol. Albuterol 2.5 mg by nebulizer causes no clinically significant increases in blood glucose in DM or CFRD patients. Diabetes patients without CF have a significantly greater increase of glucose with time (placebo or albuterol) than CFRD patients.

Pharmacological Approach to Evaluate Aerosol Pulmonary Deposition

Drug delivery to the lung in vivo may be assessed using pharmacokinetic or pharmacodynamic techniques. The choice of method depends on drug class specificities. Pharmacokinetic determination of deposition to the lung for drugs without hepatic first-pass effect, such as short acting beta2-agonists, has to be done shortly after inhalation to minimize the effect of gastrointestinal absorption. For medication undergoing important hepatic first-pass metabolisation, such as inhaled corticosteroid, plasma concentration indirectly reflects bronchial deposition. The pharmacodynamic profile should be assessed through clinical effects and adverse events induced by inhaled drugs. Dose ranking of lung deposition for bronchodilators requires patient selection with sufficient bronchial obstruction to maintain room for improvement after the first dose. To assess dose effect relationship between inhaled corticosteroid, the Finney parallel line bioassay is the reference method with a study period of at least 6 weeks. Analysis of side effects with high doses of beta2-agonists or inhaled corticosteroids may also be used to compare lung deposition. Finally, pharmacological evaluation of lung deposition provides complementary information to scintigraphic studies, based on their clinical relevance.

Dose-response to salbutamol via a novel palm sized nebuliser (Aerodose Inhaler), conventional nebuliser (Pari LC Plus) and metered dose inhaler (Ventolin Evohaler) in moderate to severe asthmatics

AIMS

The Aerodose inhaler is a novel, palm-sized, breath actuated device which requires little patient coordination. This study compared the dose-response of salbutamol delivered by the Aerodose Inhaler (Aerogen Inc., Mountain View, USA) vs Pari LC Plus jet nebulizer (Pari LC Plus; Pari GmbH, Starnberg, Germany) and Ventolin Evohaler HFA pMDI (Evohaler; Allen & Hanburys [GlaxoSmithkline], Uxbridge, UK).

METHODS

Twenty-two moderate to severe asthmatic patients, mean (s.d.) age: 44.7 (9.4), FEV(1): 58.1 (12.0), received 4 cumulative doubling doses of salbutamol in a randomised, investigator blind, balanced crossover design. Spirometry and systemic safety variables (heart rate, blood pressure, T wave amplitude, QTc interval and potassium) were measured at baseline and after each dose.

RESULTS

Parallel regression analysis revealed that microgram relative potency ratios for the Aerodose Inhaler to be five times more efficient for FEV(1) than either the Pari LC Plus (0.202, 90% CI: 0.189-0.216) or the Evohaler (0.202, 90% CI: 0.189-0.216), while there was no difference between Pari LC Plus vs Evohaler. Similarly, Aerodose Inhaler vs. Pari LC Plus showed approximately five-fold greater potency for all systemic parameters, except blood pressure. As compared to the Evohaler, Aerodose Inhaler had equivalent potency for plasma potassium and T wave amplitude, but demonstrated greater potency for heart rate and QT(c) interval.

CONCLUSIONS

This study has indicated therefore, that Aerodose Inhaler is approximately five times as efficient as the Pari LC Plus and Evohaler in relative lung delivery of salbutamol in moderate to severe asthmatics.

?2-Adrenoceptor-mediated intrinsic sympathomimetic activity of carteolol: an in vivo study

The intrinsic sympathomimetic activity (ISA) of a beta-adrenoceptor blocker can be mediated by beta(1)- or beta(2)-adrenoceptors. The aim of this study was to characterize the ISA of the beta-adrenoceptor blocker carteolol in healthy volunteers. Two approaches were employed. First, we assessed the effects of carteolol (20, 40 or 80 mg p.o.) on blood pressure, heart rate and heart-rate corrected duration of electromechanical systole (QS(2)c, a measure of cardiac contractility) in the volunteers. Carteolol dose-dependently increased systolic blood pressure, heart rate and contractility and decreased diastolic blood pressure. The beta(1)-adrenoceptor blocker bisoprolol did not attenuate these carteolol effects, but rather enhanced the effects on heart rate and systolic blood pressure. Second, we treated volunteers for 7 days with 1 x 20 mg/day carteolol and assessed lymphocyte beta(2)-adrenoceptor density (by (-)-[(125)I]-iodocyanopindolol binding) and functional responsiveness (by 10 muM isoprenaline-induced increase in lymphocyte cyclic AMP content). Carteolol significantly reduced lymphocyte beta(2)-adrenoceptor density and function. After withdrawal of carteolol lymphocyte beta(2)-adrenoceptor density and function recovered only very slowly and had not returned to control levels 11 days after carteolol withdrawal. In conclusion, the fact that, on the one hand, the cardiovascular effects of carteolol were not attenuated by the beta(1)-adrenoceptor blocker bisoprolol and, on the other, carteolol significantly decreased lymphocyte beta(2)-adrenoceptor density and function is in favour of the idea that the ISA of carteolol is mediated by beta(2)-adrenoceptors. Involvement of an additional receptor site (e.g. the propranolol-resistant state of the beta(1)-adrenoceptor), however, cannot be excluded.

Acute systemic effects of inhaled salbutamol in asthmatic subjects expressing common homozygous beta2-adrenoceptor haplotypes at positions 16 and 27

AIMS

The relationship between beta2-adrenoceptor polymorphisms at positions 16 and 27, and the acute systemic beta2-adrenoceptor effects of inhaled salbutamol is unclear. We therefore elected to evaluate the influence of common homozygous beta2-adrenoceptor haplotypes on the acute systemic beta2-adrenoceptor effects following inhaled salbutamol in asthmatic subjects.

METHODS

An initial database search of 531 asthmatic subjects identified the two commonest homozygous haplotypes at positions 16 and 27 to be Arg16-Gln27 (12%) and Gly16-Glu27 (19%). After a 1-week washout period where all beta2-adrenoceptor agonists were withdrawn, 16 Caucasian subjects (Arg16-Gln27: n = 8 and Gly16-Glu27: n = 8) were given a single dose of inhaled salbutamol (1200 microg), followed by serial blood sampling for serum potassium, along with measurements of diastolic blood pressure and heart rate, at 5-min intervals for 20 min.

RESULTS

The two groups were well matched for age, sex, FEV1, and inhaled corticosteroid dose. Baseline values for serum potassium, diastolic blood pressure and heart rate were not significantly different comparing Arg16-Gln27 vs Gly16-Glu27. The mean +/- SEM maximum serum potassium change from baseline over 20 min was significantly greater (P = 0.04) for Arg16-Gln27: -0.37 +/- 0.05 mmol l(-1) vs Gly16-Glu27: -0.23 +/- 0.04 mmol l(-1); 95% CI for difference: -0.01 to -0.28 mmol l(-1). The maximum diastolic blood pressure change from baseline over 20 min was significantly greater (P = 0.0008) for Arg16-Gln27: -13 +/- 1 mmHg vs Gly16-Glu27: -4 +/- 2 mmHg; 95% CI for difference: -5, 14 mmHg. There was no significant difference comparing the maximum heart rate change from baseline for Arg16-Gln27: 10 +/- 3 beats min(-1) vs Gly16-Glu27: 10 +/- 3 beats min(-1).

CONCLUSIONS

Caucasian asthmatic subjects with the Arg16-Gln27 haplotype exhibited a greater systemic response to inhaled salbutamol, compared with those with the Gly16-Glu27 haplotype. The attenuated beta2-adrenoceptor response in the Gly16-Glu27 haplotype would be in keeping with increased susceptibility to prior down-regulation by endogenous catecholamines.

Adverse effects of beta-agonists

Short-acting beta-adrenergic receptor agonists have pharmacologically predictable dose-related and potency-related adverse effects, including tachycardia and tremor, and they also affect serum potassium and glucose. These effects all show tolerance with continued exposure. The potential for arrhythmia is increased by comorbidity and hypoxemia. Nonpharmacologically predictable effects include airway hyperresponsiveness to nonspecific and specific stimuli, including allergen and exercise, and increased airway inflammation. Genetic variants of the beta-adrenergic receptor alter susceptibility to adverse effects of beta-agonists on airway function. The impact of the enantiomers of beta-agonists on adverse effects remains unclear. The two epidemics of asthma death among young people were temporally associated with introduction of potent short-acting beta-agonists (isoproterenol and fenoterol) and appear to be related to adverse effects of these drugs on airway function and airway hyperresponsiveness rather than to cardiotoxicity. Compared with short-acting agents, long-acting beta-agonists show similar but less pronounced pharmacologically predictable effects, and they have not been shown to increase airway hyperresponsiveness in adults. Postmarketing surveillance studies have not suggested significant adverse effects of long-acting beta-agonists on morbidity and mortality.

Beta-agonists

Beta-Agonists are a mainstay of asthma treatment. Short-acting beta-agonists are the most effective bronchodilators for rescue or quick relief of symptoms. Long-acting beta-agonists have a key role in long-term control when added to inhaled corticosteroid therapy, and are especially useful in the control of nocturnal asthma. Both types of beta-agonists may be used in the prophylaxis of exercise-induced asthma with long-acting beta-agonists providing more prolonged protection. beta-Agonists have minimal side effects and are safe when used appropriately.

Asthma medications and their potential adverse effects in the elderly: recommendations for prescribing

The incidence of drug-induced adverse effects is likely to increase as a result of advanced age and exposure of elderly patients to polypharmacy. Therefore, pharmacological therapy of asthma and chronic obstructive pulmonary disease (COPD) in the elderly patient can be potentially hazardous. beta(2)-agonists, administered as therapy for asthma and COPD, have recognised systemic sequelae, such as hypokalaemia and chronotropic effects, which may be life-threatening in susceptible patients. Adverse effects such as hypokalaemia can be aggravated by concomitant treatment with other drugs promoting potassium loss including diuretics, corticosteroids and theophyllines. In addition, relatively minor adverse events associated with the administration of beta(2)-agonists, such as tremor and blood pressure changes, may be of significance to the elderly patient leading to impairment in the quality of life. However, long-term treatment with beta(2)-agonists may reduce the incidence of drug-induced adverse effects as a result of beta-receptor subsensitivity. Oral and inhaled corticosteroids have been used for the treatment of acute asthma and COPD in the elderly patient. Long-term treatment with oral corticosteroids can result in serious systemic adverse effects such as suppressed adrenal function, bone loss, skin thinning and cataract formation. In contrast to beta(2)-agonists, oral corticosteroids can upregulate beta(2)-adrenoceptors and thereby potentiate the systemic sequelae of beta(2)-agonists. Hence, oral corticosteroids should be administered with caution for as short a duration as possible. Inhaled corticosteroids appear to be relatively well tolerated when administered at doses below approximately 1000 microg. However, larger doses of inhaled corticosteroids may affect hypothalamic-pituitary-adrenal function and bone turnover. In the case of inhaled corticosteroids, spacer devices, often used in older patients who cannot operate metered dose inhalers, can potentiate the systemic sequelae of both corticosteroids and beta(2)-agonists. The use of theophyllines in the treatment of COPD or chronic asthma is controversial. Theophyllines have a wide adverse effect profile and are prone to drug-drug interactions. The adverse effects may be mild or life threatening and include nausea and vomiting or sinus and supraventricular tachycardias. Therefore, theophyllines should be prescribed with extreme caution to elderly patients with asthma or COPD. In contrast, inhaled anticholinergic drugs such as ipratropium bromide and oxitropium bromide are generally safe in elderly patients and have useful bronchodilator function. Commonly reported adverse effects are an unpleasant taste and dryness of the mouth. When used as first-line therapy, anticholinergic drugs may optimise the bronchodilator effects of low-dose inhaled beta(2)-agonists in patients with chronic airflow obstruction, and hence obviate the need for higher doses.

Effects of aerosolized albuterol on physiologic responses to exercise in standardbreds

OBJECTIVE

To examine the effects of an aerosolized beta2-adrenoreceptor agonist, albuterol, on performance during a standardized incremental exercise test in clinically normal horses.

ANIMALS

8 Standardbred pacing mares.

PROCEDURE

Clinically normal horses, as judged by use of physical examination, hematologic findings, serum biochemical analysis, and airway endoscopy, were randomly assigned to 2 groups and were given 900 microg of albuterol via a metered-dose inhaler 30 minutes before beginning a standardized incremental exercise test in a crossover design with a 7-day minimum washout. Further examination included measurement of baseline lung mechanics, response to histamine bronchoprovocation, and bronchoalveolar lavage.

RESULTS

No significant differences (albuterol vs placebo) were seen for any incremental exercise test variables (ie, maximum oxygen consumption, maximum carbon dioxide consumption, respiratory quotient, treadmill speed at heart rate of 200 beats/min, or number of steps completed during an incremental exercise protocol). Mast cell percentage was significantly (r = -0.84) associated with the concentration of aerosolized histamine that evoked a 100% increase in total respiratory system resistance. No other direct correlations between bronchoalveolar lavage fluid cell types and any indices of exercise capacity or airway reactivity were found.

CONCLUSIONS AND CLINICAL RELEVANCE

Although no horse had exercise intolerance, 4 horses had airway hyperreactivity with bronchoalveolar lavage fluid mastocytosis; these horses may have been subclinically affected with inflammatory airway disease. In our study, albuterol did not enhance performance in 8 clinically normal racing-fit Standardbreds.

Pharmacokinetics and systemic beta2-adrenoceptor-mediated responses to inhaled salbutamol

AIMS

To examine whether systemic beta2-adrenoceptor responses, such as tachycardia, tremor and hypokalaemia, can be used as a surrogate for the 20 min pharmacokinetic profile of inhaled salbutamol.

METHODS

A retrospective analysis of eight separate published studies in healthy volunteers was performed, each with an identical protocol evaluating the early lung absorption profile of a nominal 1200 microg dose of salbutamol given by different inhaler devices. Peak postural finger tremor, plasma potassium and heart rate were assessed.

RESULTS

We found the maximum (Cmax) and average (Cav) plasma concentrations of salbutamol to be correlated (P < 0.0001) to change in plasma potassium (Cmax r = 0.904; Cav r = 0.899) and tremor (Cmax r = 0.875; Cav r = 0.857). No significant correlations existed between change in heart rate and Cmax (r = 0.425) or Cav (r = 0.415).

CONCLUSIONS

Systemic beta2-adrenoceptor responses, in particular hypokalaemia and tremor, but not heart rate, appear to be good surrogates for evaluating the lung delivery of inhaled salbutamol. Consequently it is suggested that potassium or tremor responses may be used to evaluate the relative lung delivery of salbutamol from different inhaler devices.

Subjective and objective markers of treatment response in patients with seasonal allergic rhinitis

BACKGROUND

Although there is a recognized association between upper and lower allergic airways disease, it is unknown how seasonal allergic rhinitis (SAR) therapy will effect sensitive markers of airway function in patients with no history of asthma.

OBJECTIVE

To prospectively evaluate subjective and objective markers of treatment response in 26 patients with SAR who have been screened to exclude a diagnosis of asthma.

METHODS

The patients' usual treatment, with antihistamine alone (n = 13) or in combination with intranasal corticosteroid (n = 13), was withheld for 1 week to achieve a baseline and then resumed. Measurements were made after baseline and after 2 and 4 weeks of treatment for nasal peak inspiratory flow rate (nPIFR); airways resistance (Raw) and specific conductance (sGaw); and nasal nitric oxide (NO). Patients reported their symptom (nasal, throat and eye) scores, daily activity scores, and ocular sodium cromoglycate usage over the preceding 24 hours.

RESULTS

Compared with baseline, there were significant (P < .05) improvements with nPIFR, symptom scores and cromoglycate usage at 2 and 4 weeks of treatment. There was no significant suppression for NO at 2 or 4 weeks. There was a significant correlation between nPIFR and nasal symptoms (r = -0.52, P < .001). After 4 weeks of treatment there were significant (P < .05) improvements in sGaw (143.3% predicted) and Raw (91.6% predicted) compared with baseline (sGaw: 111.8%, Raw: 104.2% predicted).

CONCLUSION

Treatment of SAR improves upper and lower airway parameters but not NO. Nasal PIFR correlates significantly with nasal symptoms.

Pharmacokinetics and pharmacodynamics of cumulative single doses of inhaled salbutamol enantiomers in asthmatic subjects

Objectives of this study were to compare the pharmacokinetics, pharmacodynamics and safety of single cumulative doses of active (R)-salbutamol given either as the single enantiomer or racemic mixture by inhalation to subjects with mild to moderate asthma. This was a double-blind, crossover, cumulative-dose, randomized study where all subjects received either four doses of 1.25 mg of (R)-salbutamol or 2.5 mg of racemic (RS-) salbutamol by nebulization. The pharmacokinetic parameters were determined by noncompartmental analysis and model-fitting. Changes in FEV(1), plasma potassium, plasma glucose, heart rate, and QTc interval were measured. The potassium and glucose data were fitted to indirect response pharmacodynamic models. The heart rate and QTc data were evaluated using data descriptors. No significant differences in pharmacokinetics of (R)-salbutamol given as either (R)- or (RS)-salbutamol were found with AUC values of 11.90 +/- 4.37 and 11. 47 +/- 2.88 ng.h/ml. The t(max)of about 2 h reflected serial dosing rather than delayed absorption. The t(1/2)averaged about 3.5 h. The (S)-salbutamol showed AUC of 48.46 +/- 12.11 ng.h/ml with a t(1/2)of about 5 h. The changes in FEV(1)reached a plateau after an initial increase and did not return to pre-drug values for 10 h. All pharmacodynamic parameters were similar whether (R)- or (RS)-salbutamol was given. The exposure to (R)-salbutamol was identical after inhalation of (R) -and (RS)-salbutamol by subjects with asthma. Several pharmacological responses including FEV(1)were also similar and there were no unique safety concerns with either treatment.

Cumulative dose response study comparing HFA-134a albuterol sulfate and conventional CFC albuterol in patients with asthma

BACKGROUND

As a result of the pending ban on chlorofluorocarbon production, the non-chlorofluorocarbon propellant 1,1,1,2-tetrafluoroethane (HFA-134a) is being evaluated as a replacement for CFCs in metered-dose inhalers.

OBJECTIVES

This cumulative dose response study compared the safety and bronchodilator efficacy of 16 cumulative inhalations of albuterol sulfate in an HFA-134a, CFC-free propellant system (108 microg of albuterol sulfate, equivalent to 90 microg of albuterol base) with that of equivalent doses of albuterol in a conventional CFC propellant system.

METHODS

Twenty-two patients with at least a 12-month history of stable asthma, who were currently taken an inhaled beta-adrenergic bronchodilator, and who had a FEV1 between 40% and 80% of predicted, were enrolled in this randomized, modified-blind, two-period crossover study. One, 1, 2, 4, and 8 inhalations of study drug were self-administered at 30-minute intervals, resulting in 16 cumulative inhalations. Pulmonary function and safety measures were assessed after each dosing interval.

RESULTS

A significant dose response was found for HFA-134a albuterol sulfate and CFC albuterol with regard to changes in FEV1, serum potassium, heart rate, and blood pressure after 16 cumulative inhalations. No significant differences were demonstrated between HFA-134a albuterol sulfate and CFC albuterol for any FEV1 or safety parameter at any cumulative dose level. No clinically meaningful laboratory or physical examination abnormalities were found with administration of either HFA-134a albuterol sulfate or CFC albuterol.

CONCLUSIONS

HFA-134a albuterol sulfate provides bronchodilation comparable to CFC albuterol and has a similar safety profile.

Onset and duration of action of single doses of formoterol inhaled via Turbuhaler

The aim of the study was to investigate the time of onset and the duration of the bronchodilating effect of different doses of formoterol administered via Turbuhaler in patients with moderate asthma. Thirty-one patients (five women) with a mean forced expiratory volume in 1 s (FEV1) of 1.97 +/- 0.54 1 and a mean reversibility of 31 +/- 14% of baseline were included in this double-blind, randomized, placebo-controlled and cross-over study. The patients inhaled single doses of placebo, i.e. 6, 12, 24, or 48 micrograms formoterol fumarate, on 5 separate days. Serial measurements of specific airways conductance (SGAW) and FEV1 were performed at regular time intervals for 12 h. The majority of the patients had at least a 50% increase in SGAW within 1-4 min after administration of all active treatments. The maximum increase in FEV1 over placebo was dose-dependent: 12% (6 micrograms), 18% (12 micrograms), 19% (24 micrograms), and 26% (48 micrograms) (P < 0.001). Twelve hours after administration of 6, 12, 24, and 48 micrograms formoterol, the mean increase in FEV1 was still 7%, 15%, 18%, and 27%, respectively, above the value following placebo. Headache was the most frequently reported adverse event in all treatments including placebo. After inhalation of 48 micrograms, three patients experienced mild tremor lasting for less than 1 h; likewise, one patient experienced the same event for 3 h after placebo. Formoterol administered via Turbuhaler10 gave a rapid and dose-related bronchodilating effect lasting for 12 h and was well tolerated.

Early lung absorption profile of non-CFC salbutamol via small and large volume plastic spacer devices

AIMS

To evaluate the lung dose of a non-CFC salbutamol metered dose inhaler (MDI) formulation via three commonly used plastic spacer devices, of both large and small volume, compared with the MDI used on its own.

METHODS

Ten healthy volunteers were studied in a randomized single (investigator) blind crossover design. Single 1200 microg nominal doses of salbutamol from a non-CFC MDI (Airomir), as 12 sequential 100 microg puffs over 6 min, were delivered from the MDI alone and via two large volume spacer devices (Nebuhaler, Volumatic), and a small volume spacer (Aerochamber). All spacers were prewashed prior to each study day and mouth rinsing was performed after each drug sequence. Plasma salbutamol was measured at 5, 10, 15 and 20 min, with calculation of maximum (Cmax) and average (Cav) concentrations. This lung dose was assessed using the early lung absorption profile of salbutamol in the first 20 min after inhalation.

RESULTS

Both of the large volume spacers, the Nebuhaler and the Volumatic, delivered significantly more salbutamol than the MDI alone. For Cav this amounted to a 2.07-fold difference (95% CI 1.48-2.90) between Nebuhaler vs MDI, and a 1.49-fold difference (95%CI 1.19-1.87) between Volumatic vs MDI. The Nebuhaler also produced greater deposition than either the Volumatic or the Aerochamber spacers; Nebuhaler vs Volumatic: 1.39-fold difference (95% CI 1.09-1.76), Nebuhaler vs Aerochamber: 1.63-fold difference (95% CI 1.20-2.21). There were no significant differences between the Aerochamber and the MDI alone.

CONCLUSIONS

Using the early lung absorption profile, for administration of the same nominal dose, both of the large volume spacers (Nebuhaler and Volumatic) but not the small volume spacer (Aerochamber) delivered significantly more salbutamol than the MDI alone. The Nebuhaler also produced greater delivery than either the Volumatic or the Aerochamber spacer devices. Our results show that whilst lung delivery of non-CFC salbutamol MDI is improved by the use of a plastic spacer, there may be appreciable differences in performance, particularly between large and small volume devices.

Safety and efficacy of a high cumulative dose of salbutamol inhaled via Turbuhaler or via a pressurized metered-dose inhaler in patients with asthma

An open, crossover and randomized study was carried out to compare the safety and efficacy of salbutamol inhaled using the dry-powder inhaler Turbuhaler, and using a pressurized metered-dose inhaler (pMDI). Twelve patients with moderate to severe asthma, aged 47-68 years, were included in the study. On two separate days, patients received a total dose of 1600 micrograms of salbutamol administered in a cumulative dose fashion: 100, 100, 200, 400 and 800 micrograms at 3-min intervals. Salbutamol inhaled via Turbuhaler caused a larger decrease in serum potassium concentration than did salbutamol inhaled via pMDI. The estimated relative dose potency of the hypokalaemic effect of salbutamol Turbuhaler vs salbutamol pMDI was 2.0 with a 95% confidence interval of 1.3-3.6. Turbuhaler caused a small (but statistically significantly greater than with pMDI) increase in heart rate, QTc interval and tremor. Blood pressure was unaffected by the treatments. No adverse events of clinical relevance were reported. The estimated relative dose potency of the bronchodilating effect (FEV1) of salbutamol Turbuhaler vs salbutamol pMDI was 3.0 with a 95% confidence interval of 1.8-5.8. In conclusion, salbutamol inhaled via Turbuhaler was more potent and seemed to have a better therapeutic ratio than salbutamol inhaled via pMDI. Both treatments were equally well tolerated.

Lung delivery of non-CFC salbutamol via small volume metal spacer and large volume plastic spacer devices compared with an open vent jet nebulizer

AIMS

To compare the lung delivery of salbutamol from a commonly used constant output open vent jet nebuliser (Sidestream) with use of both a conventional large volume plastic spacer (Volumatic) and a novel small volume metal spacer (NebuChamber). This was assessed using the early lung absorption profile of salbutamol over the first 20 min after inhalation.

METHODS

Twelve healthy volunteers were studied in a randomized single (investigator) blind crossover design. Single 1200 microg nominal doses salbutamol from a CFC-free metered-dose inhaler (12 sequential 100 microg puffs of Airomir) were delivered via the Volumatic and NebuChamber spacers. A single 1200 microg nominal dose of salbutamol was given as a 4 ml fill volume from a Sidestream nebuliser with mouthpiece. Mouth rinsing was performed after each drug sequence. Plasma salbutamol was measured at 5, 10, 15 and 20 min after the last dose of each inhalation sequence, with calculation of maximal concentration (Cmax) and average concentration over 20 min (C[av]). Systemic beta2-responses were measured as plasma potassium, tremor and heart rate.

RESULTS

Both the Volumatic and the NebuChamber spacers produced significantly greater salbutamol concentration than the Sidestream nebuliser. For C(av) this amounted to a 7.34-fold difference (95%CI 5.31 to 9.38) between Volumatic vs Sidestream, and a 7.04-fold difference (95%CI 4.91 to 9.17) for NebuChamber vs Sidestream. Similar differences were found for the extrapulmonary beta2-responses. There were no significant differences in either salbutamol concentration or extrapulmonary beta2-responses between the Volumatic and NebuChamber spacers.

CONCLUSIONS

We found that, in vivo, both the Volumatic and the NebuChamber spacers produced seven-fold greater lung delivery of salbutamol than the Sidestream nebuliser when comparing microgram equivalent nominal doses, in terms of the early lung absorption profile.

Effects of airway calibre on lung delivery of nebulised salbutamol

BACKGROUND

A study was undertaken to test the hypothesis that airway calibre may alter lung deposition and therefore lung bioavailability of inhaled drugs as a result of narrowed airways reducing peripheral drug delivery. This was evaluated using the early lung absorption profile of salbutamol over the first 30 minutes after inhalation.

METHODS

Three groups were compared: (1) 10 normal subjects with mean forced expiratory volume in one second (FEV1) 109.5% predicted and mid forced expiratory flow (FEF25-75) 103.0%, (2) 10 mild asthmatic patients with FEV1 102.0% and FEF25-75 82.6%, and (3) 10 severe asthmatic patients with FEV1 49.2% and FEF25-75 27.5% predicted. Each subject had one study visit where a single dose of nebulised salbutamol was given (40 micrograms/kg) via a Ventstream nebuliser with mouthpiece followed by mouth rinsing. Plasma salbutamol levels were measured at five, 10, 20, and 30 minutes after the end of nebulisation with calculation of maximal (Cmax) and average (Cav) concentration over 0-30 minutes. Systemic beta 2 responses (plasma potassium, tremor and heart rate) and airway responses (FEV1, FEF25-75) were measured before and 30 minutes after nebulisation.

RESULTS

For Cav over 0-30 minutes the severe asthmatic patients had a lower plasma salbutamol concentration (1.31 ng/ml) than either the normal subjects (2.40 ng/ml) or those with mild asthma (2.45 ng/ml): normal subjects versus severe asthmatics 95% CI 0.30 to 1.88, mild versus severe asthmatics 95% CI 0.07 to 2.21. Airway responses as delta FEF25-75 were lower in the severe asthmatic subjects (0.30 l/s) than in either the normal subjects (0.69 l/s) or those with mild asthma (0.74 l/s): normal subjects versus severe asthmatic subjects 95% CI 0.09 to 0.88, mild versus severe asthmatics 95% CI 0.04 to 0.93. Values for delta log tremor also showed attenuated responses in those with severe asthma (1.22 mg2/s) compared with normal subjects (2.00 mg2/s) or those with mild asthma (2.02 mg2/s): normal subjects versus those with severe asthma 95% CI -0.02 to 3.30, mild versus severe asthmatics 95% CI 0.02 to 3.30.

CONCLUSIONS

These results show that baseline airway calibre significantly alters the early lung absorption profile of salbutamol in patients with severe asthma. This may have implications in terms of optimising dose and delivery of inhaled beta 2 agonists in these patients.

Partial pulmonary sympathetic denervation by thoracoscopic D2-D3 sympathicolysis for essential hyperhidrosis: effect on the pulmonary diffusion capacity

In patients with essential hyperhidrosis (EH), a pathological condition characterized by increased activity of the upper dorsal sympathetic ganglia D2-D3, anatomical interruption at the D2-D3 level by thoracoscopic sympathicolysis (TS) is a safe and effective treatment. The D2 and D3 ganglia, however, are also in the pathway of sympathetic lung innervation, which may influence the pulmonary diffusion capacity for carbon monoxide (expressed as transfer factor for CO:TLCO, and as transfer coefficient for CO:KCO). We therefore studied the effect of TS on TLCO and KCO in 50 EH patients: compared with pre-operative values, both TLCO (-6.7%, P < 0.001) and KCO (-4.2%, P = 0.002) were significantly decreased at 6 weeks after bilateral TS, an effect which was independent of the smoking status of the patients. In order to explain this phenomenon, the following pharmacological interventions were studied: (1) oral beta 1 + 2-adrenoreceptor blockade with propranolol caused a comparable decrease of TLCO (-6.3%) and KCO (-7.5%) in matched normal subjects, but had no effect on TLCO and KCO in EH patients prior to TS; and (2) subsequent inhalation of the beta 2-adrenoreceptor agonist salbutamol in a dosage suspected to cause alveolar beta-receptor stimulation had no effect on TLCO and KCO, neither in the normal subjects, nor in EH patients (before and after TS). Although the exact mechanism of the TS-induced decrease in TLCO and KCO remains speculative, these findings suggest that they may be related to a beta 1-adrenoreceptor-mediated change in pulmonary capillary membrane permeability, although TS-induced changes in pulmonary blood flow or an interplay of both mechanisms cannot be excluded.

Pharmacokinetics and extrapulmonary beta 2 adrenoceptor activity of nebulised racemic salbutamol and its R and S isomers in healthy volunteers

BACKGROUND

Racemic salbutamol remains one of the most commonly used bronchodilators in the treatment of reversible airways obstruction. Data from animal and human studies suggest that the S-isomer, whilst contributing no bronchodilator activity, may induce increased bronchial hyperreactivity and may explain the adverse effects of regular racemic salbutamol on asthmatic disease control. The purpose of this study was to evaluate the dose-response effects of racemic (+/-) salbutamol and its R(-) and S(+) isomers in terms of pharmacokinetics and pharmacodynamics at extrapulmonary beta 2 adrenoceptors when given by the inhaled route to healthy volunteers.

METHODS

Twelve healthy volunteers of mean age 20.6 years were studied in a double blind, placebo controlled, crossover design comparing cumulative doubling doses of nebulised R-salbutamol (R) and S-salbutamol (S) isomers (200 micrograms/400 micrograms/800 micrograms/1600 micrograms/3200 micrograms) and racemic salbutamol (RS) (400 micrograms/800 micrograms/1600 micrograms/3200 micrograms/6400 micrograms). Doses were administered at 20 minute intervals (t0/t20/t40/t60/t80) and measurements were made of extrapulmonary beta 2 responses as an increase in finger tremor and heart rate and fall in plasma potassium at baseline and each dose level (t0/t20/t40/t60/t80/t100). Plasma levels of salbutamol were measured at 15 minutes after each dose with a further sample at 30 minutes after the last dose (t110).

RESULTS

Pharmacodynamics showed dose related beta 2 responses for R-salbutamol and RS-salbutamol but not for the S isomer, and a plateau in response was not reached within the administered dose range. No differences in responses were found between R-salbutamol and RS-salbutamol when compared on a 1:2 microgram basis. The effects of the S isomer were indistinguishable from those of placebo. For all beta 2 responses there were differences between R-salbutamol and S-salbutamol (for t100 response as change from placebo); tremor (log units): R 0.74 vs S 0.03 (95% CI 0.39 to 1.03); fall in potassium (mmol/ 1): R 0.35 vs S -0.02 (95% CI 0.03 to 0.71). Pharmacokinetics showed consistently higher levels for S-salbutamol than R-salbutamol at 15 minutes after each dose, with R-salbutamol already being cleared and S-salbutamol reaching peak levels at 30 minutes after the last dose (at t110). There were higher plasma levels of R-salbutamol and S-salbutamol following administration of the respective isomers alone compared with their levels after administration of the racemate, suggesting an influence of each isomer on the clearance of the opposite isomer when given as a racemate.

CONCLUSIONS

The S-isomer of salbutamol has no detectable activity at extrapulmonary beta 2 adrenoceptors whilst exhibiting higher plasma levels than the R-isomer, in keeping with greater clearance of R-salbutamol than S-salbutamol. Inhalation of R-salbutamol and RS-salbutamol produced dose-related beta 2 responses which were equivalent when compared on a 1:2 microgram basis, despite higher plasma levels of R-salbutamol after administration of the R isomer than after administration of the racemate. Further dose ranging studies are required at steady state to evaluate the pharmacokinetics of R- and S-salbutamol and their relative effects on bronchial hyperreactivity when given on a regular basis to asthmatic subjects.

Dose-response of inhaled drugs in asthma. An update

The demographic characteristics of patients used in clinical trials (such as the severity of airway obstruction) can significantly influence the results of dose-response studies, emphasising the need to evaluate effects on the steep part of the dose-response curve. Differences in inhaler devices can also influence study outcomes, as for inhaled drugs both airway efficacy and adverse effect profiles are primarily determined by lung deposition and hence bioavailability. Dose-response studies with short- and long-acting beta 2-agonists show an excellent therapeutic ratio at conventional doses used in everyday clinical practice (i.e. 2 to 4 puffs). Dose-related systemic effects of beta 2-agonist occur at higher doses, for salbutamol (albuterol) > 500 micrograms. Fenoterol is a beta 2-agonists with higher intrinsic activity than salbutamol and produces greater systemic effects at higher than conventional doses on a microgram equivalent basis, although even at 4000 micrograms such differences are unlikely to be clinically relevant. No differences between fenoterol and salbutamol have been shown in terms of bronchodilator potency on a microgram equivalent basis. The long-acting beta 2-agonist salmeterol, as a partial agonist, has the potential to attenuate the acute bronchodilator response to a higher activity beta 2-agonist such as salbutamol or fenoterol, although there is no evidence to date on whether this is relevant in the setting of acute asthma. When comparing inhaled corticosteroids, attention should be focused on their respective risk-benefit ratios for antiasthmatic versus systemic activity. In terms of detecting systemic activity, it is important to use sensitive measures, such as urinary cortisol excretion, rather than insensitive parameters, such as a single morning plasma cortisol measurement between 0800h and 1000h. For fluticasone, a greater in vitro potency results in only marginal differences in antiasthmatic efficacy, particularly on the flatter part of the dose-response curve above 1000 micrograms/day in adults and 400 micrograms/day in children. However, the same enhanced potency translates directly into commensurate differences in systemic adverse effects on the steep part of the systemic dose-response curve above 1000 micrograms/day in adults and 400 micrograms/day in children, respectively. Furthermore, with repeated twice-daily administration, a longer elimination half-life and prolonged systemic tissue retention due to enhanced lipophilicity will result in greater systemic activity observed at steady-state in long term administration studies. This dissociation of airway and systemic dose-response curves results in a J-shaped curve for benefit: risk ratio, with a watershed area above 1000 microgram/day in adults. This fall in the benefit: risk ratio is likely to be greater for fluticasone than for budesonide or beclomethasone. Further studies are needed to clearly define the dose-response relationships of higher potency steroids such as fluticasone, particularly on the steep part of the curve (for clinical efficacy), using the appropriate back-titration design along with sensitive measures of antiasthmatic and systemic activity.

Effect of multiple actuations, delayed inhalation and antistatic treatment on the lung bioavailability of salbutamol via a spacer device

BACKGROUND

The aim of this study was to extend previous in vitro observations regarding the effects of multiple actuations of aerosols into spacer devices, delayed inhalation, and antistatic treatment of spacer devices on the amount of drug delivered for inhalation. An in vivo study of lung bioavailability of salbutamol from a large volume (Volumatic) spacer was conducted.

METHODS

Ten healthy volunteers of mean age 20.5 years with a mean forced expiratory volume in one second of 112.1% predicted were studied in a randomised single blind (investigator blind) crossover study. 1200 micrograms of salbutamol was given with mouth rinsing (100 micrograms/puff) on four study days: single puffs via spacer, multiple puffs via spacer (3 x 4 puffs), single puffs with 20 second delay before inhalation via spacer, and single puffs via an antistatic treated spacer. All spacers, including those treated with antistatic, were prewashed prior to each study day. Measurements of lung bioavailability were made at five, 10, and 20 minutes after inhalation to determine peak (Cmax) and average (Cav) plasma salbutamol levels. Systemic beta 2 responses including finger tremor, heart rate, and plasma potassium levels were also evaluated.

RESULTS

Single puffs from the spacer produced higher plasma salbutamol levels and greater systemic beta 2 responses than either multiple puffs or single puffs with delayed inhalation for a 1200 micrograms dose. For Cmax this amounted to a 1.93-fold (95% CI 1.68 to 2.19) greater lung bioavailability for single puffs than for multiple puffs and a 1.80-fold (95% CI 1.59 to 2.00) greater lung bioavailability for single puffs than for single puffs with a 20 second delay. Comparison of the normal and antistatic treated spacers (both prewashed) revealed differences for Cmax with levels 1.23-fold (95% CI 1.04 to 1.41) greater for the normal spacer.

CONCLUSIONS

Delayed inhalation from a Volumatic spacer and the use of multiple puffs results in a considerable decrease in the delivery of salbutamol to the lungs with an approximate twofold reduction in lung bioavailability. Washing a Volumatic spacer is as effective as an antistatic lining in reducing the effects of static charge on salbutamol delivery in vivo.

Salbutamol antagonizes insulin- and sodium mercaptoacetate-induced but not 2-deoxy-D-glucose-induced hyperphagia

The role of beta-adrenoreceptors in modulating feeding in glucoprivation- and lipoprivation-induced hyperphagias was studied in rats by measuring the efficacy of the selective beta2-adrenoreceptor agonist salbutamol to antagonize the hyperphagic response induced by injection of 2-deoxy-D-glucose (2-DG), insulin, or sodium mercaptoacetate (MA). 2-DG and insulin are blockers of glucose utilization, and their administration stimulates receptor cells that are selectively sensitive to central glucose availability. MA stimulates feeding in rats maintained on a fat-supplemented diet, by blocking fatty acid oxidation at different levels in the metabolic pathway. We found that salbutamol dose-dependently antagonized both the insulin- and MA-induced hyperphagia, with reductions in food intake up to 100% compared with rats treated with insulin or MA alone. On the contrary, salbutamol, even at the highest dose (15 mg/kg, IP), was completely ineffective against 2-DG-induced hyperphagia. The present results support the previously proposed notion that there are different neuronal or humoral circuits underlying the hyperphagic responses to the metabolic stimuli induced by glucoprivation (i.e., 2-DG and insulin administration), and they extend our knowledge on the effects of salbutamol on glucoprivic and lipoprivic control of feeding.

Effects of prior treatment with salmeterol and formoterol on airway and systemic beta 2 responses to fenoterol

BACKGROUND

Previous studies have shown that both salmeterol and formoterol act as partial beta 2 receptor agonists in terms of antagonising the extrapulmonary responses to fenoterol in normal subjects. The aim of the present study was to extend previous observations in evaluating the effect of prior treatment with salmeterol and formoterol on bronchodilator responses to fenoterol, a full beta 2 receptor agonist, in patients with asthma.

METHODS

Ten stable asthmatic patients of mean (SE) age 37 (3.7) years and forced expiratory volume in one second (FEV1) 59.5 (4.1)% of predicted completed the study. One hour after inhaling single doses of placebo, salmeterol 25 micrograms, or formoterol 12 micrograms, dose-response curves to repeated doses of inhaled fenoterol were constructed (cumulative doses of 100-3200 micrograms). Measurements of airway and systemic beta 2 receptor mediated responses were made at baseline, after inhalation of placebo, salmeterol, or formoterol, and after each dose of fenoterol.

RESULTS

Salmeterol and formoterol produced significant bronchodilation compared with placebo (mean difference and 95% CI compared with placebo): FEV1, salmeterol 0.41 (95% CI 0.13 to 0.69) 1, formoterol 0.47 (95% CI 0.19 to 0.75) 1. Salmeterol and formoterol had no significant effect on systemic responses compared with placebo. There were no significant differences in peak airway responses to fenoterol after treatment with salmeterol or formoterol compared with placebo (mean (pooled SE)): FEV1, placebo 2.84 (0.03) 1, salmeterol 2.87 (0.03) 1, and formoterol 2.88 (0.03) 1. There were no significant differences in the area under the dose-response curve for any of the parameters during the dose-response curve following treatment with salmeterol or formoterol compared with placebo. There was no difference in the slope of the dose-response curves to fenoterol for FEV1 or forced expiratory flow (FEF25-75) after treatment with salmeterol or formoterol compared with placebo, although there was a significant (p < 0.05) attenuation of the slope in the dose-response curve for the peak expiratory flow rate (PEFR).

CONCLUSIONS

Prior treatment with low doses of salmeterol or formoterol does not significantly alter bronchodilator dose-response curves to repeated doses of fenoterol in stable asthmatic patients.

Lung bioavailability of chlorofluorocarbon free, dry powder and chlorofluorocarbon containing formulations of salbutamol

With the future advent of a world wide ban on chlorofluorocarbon containing aerosols, a study was designed to compare the in vivo lung bioavailability of salbutamol via chlorofluorocarbon-containing metered-dose inhaler (CFC), chlorofluorocarbon-free metered-dose inhaler (CFC-free), and dry powder inhaler (DPI). Twelve healthy male subjects were given 1200 micrograms salbutamol and measurements made of plasma and urinary salbutamol. CFC-free produced significantly higher plasma salbutamol levels (ng ml-1; mean and 95% CI for difference) than either CFC or DPI: Cmax, CFC-free 4.18 vs CFC 3.29 (95% CI 0.10-1.68), vs DPI 3.42 (95% CI -0.03-1.56). The ratio for the difference in Cmax between CFC and CFC-free formulations was 1.32 (95% CI 1.02-1.61). There were no significant differences between CFC and DPI formulations. Urinary salbutamol results did not reveal any significant differences between the three inhalers (micrograms 30 min-1): CFC-free 42.4, CFC 43.8, DPI 45.3. Thus, the lung bioavailability of CFC-free was greater than that of CFC or DPI formulations of salbutamol.

Lung bioavailability of generic and innovator salbutamol metered dose inhalers

BACKGROUND

The aim of this study was to determine whether significant differences exist in lung bioavailability between generic (Salamol, Salbulin) and innovator (Ventolin) formulations of inhaled salbutamol given by metered dose inhalers.

METHODS

Ten healthy volunteers of mean age 20.5 years with a forced expiratory volume in one second (FEV1) of 112.1% predicted were studied in a randomised double blind single dosing crossover study. Salbutamol, 1200 micrograms, was given with mouth rinsing and lung bioavailability was assessed by measuring plasma salbutamol levels and urine excretion of salbutamol.

RESULTS

No differences were seen between innovator and generic salbutamol metered dose inhalers in plasma salbutamol levels, urinary salbutamol excretion, or extrapulmonary beta 2 activity. The maximum plasma salbutamol concentration (mean Cmax) and time to maximum concentration (median Tmax) were: Ventolin (2.93 ng/ml, 10 minutes), Salbulin (3.01 ng/ml, 10 minutes), Salamol (3.33 ng/ml, 10 minutes). The geometric mean ratio and 95% confidence interval for Cmax were: Salbulin/Ventolin 1.02 (0.69 to 1.41) and Salamol/Ventolin 1.13 (0.94 to 1.35).

CONCLUSIONS

No differences are apparent between the two generic and innovator formulations of salbutamol metered dose inhaler in terms of lung bioavailability.

Evaluation of the beta 2 adrenoceptor agonist/antagonist activity of formoterol and salmeterol

BACKGROUND

Salmeterol and formoterol have a lower intrinsic activity at beta 2 receptors than isoprenaline in human bronchus in vitro. The aim of the present study was to evaluate in vivo the beta 2 agonist/antagonist activity of salmeterol and formoterol at rest with low endogenous adrenergic tone, on exercise with raised endogenous adrenergic tone, and in the presence of fenoterol, an exogenous full beta 2 receptor agonist.

METHODS

Eight normal subjects were randomised to receive single doses of placebo, salmeterol 300 micrograms, formoterol 72 micrograms, or propranolol 80 mg at weekly intervals. beta 2 adrenoceptor responses were evaluated at rest, at peak exercise, and after treatment with fenoterol 2.4 mg.

RESULTS

At rest salmeterol and formoterol exhibited equivalent beta 2 agonist activity with regard to decrease in serum potassium levels and increase in finger tremor, with propranolol having no effect. Salmeterol and formoterol, like propranolol, potentiated the hyperkalaemic delta response to exercise compared with placebo, consistent with beta 2 antagonism: (mean difference and 95% confidence interval (CI) compared with placebo) salmeterol 0.20 (0.02 to 0.38) mmol/l, formoterol 0.17 (0.00 to 0.34) mmol/l, propranolol 0.45 (0.08 to 0.82) mmol/l. Propranolol blunted the heart rate delta response to exercise, consistent with beta 1 blockade, whilst salmeterol and formoterol had no effect. Salmeterol and formoterol, like propranolol, attenuated the hypokalaemic, tremor, and heart rate delta responses to fenoterol compared with placebo, in keeping with beta 2 blockade: potassium, salmeterol 0.18 (0.0 to 0.36) mmol/l, formoterol 0.17 (-0.03 to 0.37) mmol/l, propranolol 0.80 (0.54 to 1.06) mmol/l; tremor, salmeterol -0.69 (-1.26 to -0.12) log units, formoterol -0.71 (-1.53 to 0.11) log units, propranolol -0.85 (-1.66 to -0.04) log units; heart rate, salmeterol -6 (-13 to 1) beats/min, formoterol -10 (-19 to -1) beats/min, propranolol -18 (-29 to -7) beats/min.

CONCLUSIONS

At rest with low endogenous adrenergic tone salmeterol and formoterol showed equivalent beta 2 mediated agonist activity in terms of serum potassium and finger tremor responses. In the presence of raised endogenous adrenergic tone at peak exercise and in the presence of fenoterol (an exogenous full beta 2 receptor agonist), salmeterol and formoterol, like propranolol, exhibited beta 2 receptor antagonism as evidenced by their attenuation of beta 2 receptor mediated responses. The degree of beta 2 blockade with formoterol and salmeterol was comparable but less than with propranolol. The relevance of these findings at extrapulmonary beta 2 receptors with regard to airway beta 2 responses remains unclear and warrants further investigation.

Acute safety of the CFC-free propellant HFA-134a from a pressurized metered dose inhaler

The acute safety of the alternative chlorofluorocarbon-free (CFC-free) propellant HFA-134a from a pressurized metered-dose inhaler (MDI) was assessed in 12 healthy male subjects according to a double-blind, randomized, crossover design. On each of three consecutive days, cumulative doses of 1,2,4,8 and 16 inhalations were administered 30 min apart from one of three MDIs. The three MDIs contained either the HFA-134a CFC-free system without drug (HFA-Placebo), the CFC-free system with salbutamol sulphate (HFA-Salbutamol), or a conventional CFC propellant mixture without drug (CFC-Placebo). Pulmonary function (FEV1, FEF25-75%), cardiovascular performance (heart rate and blood pressure), objective tremor measurements and serum potassium were measured after each incremental dose. Similar responses for pulmonary function, cardiovascular performance, tremor and serum potassium were observed between the HFA-Placebo and CFC-Placebo groups. No statistically significant difference was seen in change from baseline of any parameter between the two propellant systems. The administration of HFA-Salbutamol produced statistically significant dose-related increases in heart rate, systolic blood pressure and tremor and a significant dose-related decrease in serum potassium; these responses were expected based on cumulative doses of active drug. Blood samples for HFA-134a analysis were collected to measure systemic absorption of this propellant. Levels of HFA-134a between 200 and 700 ng.ml-1 were detected in all subjects given the CFC-free system. This study shows that acute inhalation of HFA-134a in a CFC-free system is as safe as a CFC propellant system. Salbutamol sulphate in the CFC-free system can be delivered in a dose-linear fashion, without any noticeable change in the safety profile of active drug.

Salbutamol and high-intensity treadmill running in nonasthmatic highly conditioned athletes

Salbutamol is a widely used drug among elite athletes. We wanted to provide more information on the effects of salbutamol in nonasthmatic athletes. Seventeen highly conditioned male athletes (VO2max > 70 ml.kg-1.min-1) participated in a randomized, double-blind and placebo-controlled cross-over study. Nebulized salbutamol (0.05 mg/kg) or placebo was inhaled prior to a high intensity (110% of VO2max) treadmill run to exhaustion. The measured variables included endurance time, oxygen uptake, ventilation, breathing rate, heart rate, and oxygen saturation. Lung function was measured as forced expiratory volume in the first second (FEV1) before and after medication, and during the recovery from the run. The high intensity runs led to total exhaustion after 4-10 min. A close-to-significant shortening in endurance time was found when salbutamol was given. During the running (0-4 min) the oxygen uptake was slightly lower and the heart rate was slightly higher when salbutamol was given. No differences were found in peak oxygen uptake, peak heart rate, ventilation, breathing rate or oxygen saturation. FEV1 reflected an increase in airway caliber after the inhalation of salbutamol. These changes were still present in the recovery from the test run with the exception of the measurement immediately after the exercise. Although evidence for beta-adrenergic stimulation was found, it was concluded that a therapeutic dose of nebulized salbutamol does not improve performance in highly trained athletes during a high-intensity run to exhaustion.

Bronchodilator subsensitivity to salbutamol after twice daily salmeterol in asthmatic patients

In view of current concerns about use of regular beta-2 agonists, and the place of the newer long-acting drugs, we decided to evaluate whether continuous exposure to twice daily salmeterol results in a blunting of the acute bronchodilator response to repeated doses of salbutamol, as might be administered in the management of an acute asthma attack. After a 2 week run-in without beta-2 agonists, 17 asthmatic patients (mean [SE] age 34 [3] years, mean forced expiratory volume in 1 s [FEV1] 64 [2.7]% of predicted) were randomised to receive salmeterol 50 micrograms twice daily or placebo for 4 weeks in a double-blind cross-over fashion. A histamine challenge test was done 12 h after the last dose of each treatment period, and dose-response curves to inhaled salbutamol (200-3200 micrograms) were constructed 36 h after the last dose. Patients treated with salmeterol had reduced bronchodilator responses to salbutamol in terms of FEV1 and peak expiratory flow rate (PEFR) than those treated with placebo. The reduction in response equated with a 2.5-fold and a fourfold greater dose of salbutamol being required to produce a given FEV1 and PEFR, respectively. There was a significant reduction in lymphocyte beta-2 adrenoceptor density after salmeterol compared with placebo and run-in. Salmeterol remained effective in terms of disease control, with a significant improvement in morning PEFR compared with placebo that was maintained over the 4 week treatment period.(ABSTRACT TRUNCATED AT 250 WORDS)

Subsensitivity of bronchodilator and systemic beta 2 adrenoceptor responses after regular twice daily treatment with eformoterol dry powder in asthmatic patients

BACKGROUND

There is controversy as to the role of long acting beta 2 agonists such as eformoterol and, in particular, whether bronchodilator tolerance occurs during continuous therapy. The purpose of this study was to extend previous observations of bronchodilator subsensitivity with metered dose eformoterol aerosol in order to assess whether tolerance also occurs with a dry powder formulation of the same drug.

METHODS

Sixteen asthmatic patients of mean age 33 (range 18-53) years and FEV1 (% predicted) of 64 (3)%, of whom 13 were receiving inhaled corticosteroids, received regular treatment with eformoterol 24 micrograms twice daily or placebo twice daily (without beta 2 agonists) given concurrently for four weeks in a randomised double blind cross-over design. An initial two week run-in was used when beta 2 agonists were withdrawn and substituted with ipratropium bromide. Dose-response curves to eformoterol (cumulative dose 6-102 micrograms) for airways and systemic beta 2 responses were constructed at the end of each treatment period.

RESULTS

Baseline values for airways and systemic responses were similar. The peak delta FEV1 response from the dose-response curve (as change from baseline) and the delta response for FEV1 and FEF25-75 at six hours after the last dose were attenuated after eformoterol compared with placebo: peak delta FEV1 response 1.001 with placebo v 0.841 with eformoterol (95% CI 0.04 to 0.28); at six hours 0.931 with placebo v 0.581 with eformoterol (95% CI 0.20 to 0.50); and for delta FEF25-75 at six hours 1.29 1/s with placebo v 0.87 1/s with eformoterol (95% CI 0.15 to 0.69). Morning peak expiratory flow rate was significantly improved during treatment with eformoterol (451 1/min) compared with placebo (399 1/min) (95% CI 21 to 82). Systemic beta 2 responses were blunted after eformoterol, together with a reduction in lymphocyte beta 2 receptor binding density.

CONCLUSIONS

Regular twice daily eformoterol dry powder may produce bronchodilator subsensitivity in terms of both peak and duration of response to cumulative repeated doses of eformoterol. Systemic beta 2-mediated adverse effects also showed tolerance, which was mirrored by downregulation of lymphocyte beta 2 adrenoceptors.

Expression of the beta 2 adrenoceptor partial agonist/antagonist activity of salbutamol in states of low and high adrenergic tone

BACKGROUND

Salbutamol exhibits partial agonist/antagonist activity at airway beta 2 receptors in vitro in that it attenuates the bronchorelaxant effect of the full agonist isoprenaline. The aim of the present study was to characterise the partial beta 2 agonist/antagonist activity of salbutamol in vivo during supine rest and exercise, in states of low and high adrenergic tone.

METHODS

Eight normal subjects were randomised to receive single oral doses of salbutamol 2 mg, 4 mg, 8 mg (S2, S4, S8), placebo (PL), or propranolol 80 mg (PR). The beta 2 adrenoceptor responses were evaluated after supine rest and subsequently in response to maximal exercise.

RESULTS

Salbutamol demonstrated a dose-related increase in resting heart rate and tremor and a fall in serum potassium level consistent with beta 2 agonism. On exercise, the hyperkalaemic response was augmented by propranolol compared with placebo consistent with beta 2 blockade: mean difference for delta response (95% CI) PR v PL was 0.60 (0.02 to 1.27) mmol/l. This effect also occurred with salbutamol in a dose-related fashion: S8 v PL 0.33 (0.01 to 0.71) mmol/l, S8 v S2 0.31 (-0.02 to 0.61) mmol/l. Whilst propranolol blunted exercise heart rate in keeping with beta 1 blockade, salbutamol had no effect. Exercise produced an increase in lymphocyte beta 2 receptor binding density (Bmax) which was not affected by salbutamol. Plasma levels of adrenaline and noradrenaline at peak exercise were also unaltered by salbutamol in comparison with placebo.

CONCLUSIONS

In a state of low adrenergic tone at rest salbutamol produces effects consistent with beta 2 agonism. In contrast, in a state of increased adrenergic tone during exercise salbutamol produced beta 2 selective antagonism as evidenced by its effects on exercise-induced hyperkalaemia (beta 2) but not on exercise-induced tachycardia (beta 1). The effects of salbutamol on beta 2 receptor density do not explain its effects on exercise-induced hyperkalaemia since upregulation rather than downregulation was observed. This in vivo phenomenon of partial beta 2 agonist/antagonist activity of salbutamol may be of relevance in the setting of acute asthma if adrenergic tone is increased.

Comparison of the relative airways and systemic potencies of inhaled fenoterol and salbutamol in asthmatic patients

BACKGROUND

There is controversy as to the relative safety of fenoterol and salbutamol. No differences have been found in the relative cardiac beta 1/beta 2 receptor activity of inhaled fenoterol and salbutamol in normal subjects. These initial findings have been extended by comparing the respective potencies of equivalent doses by weight of fenoterol and salbutamol in asthmatic subjects, in terms of airways and systemic responses.

METHODS

Eighteen asthmatic patients of mean (SD) age 40 (14) years and a forced expiratory volume in one second (FEV1)% predicted of 56 (14)% (1.97 (0.66)1) were randomised to inhale fenoterol (100 micrograms/puff or 200 micrograms/puff), salbutamol, or placebo (100 micrograms/puff or 200 micrograms/puff) on three separate days. Dose-response curves were constructed using cumulative doses of 100 micrograms, 200 micrograms, 400 micrograms, 1000 micrograms, 2000 micrograms, and 4000 micrograms, and airways and systemic responses were measured 20 minutes after each dose with 40 minute increments. Dose ratios for the relative potency of fenoterol versus salbutamol were calculated from the dose-response curves using regression analysis of parallel slopes.

RESULTS

There was no difference in bronchodilator potency between fenoterol and salbutamol (as median dose ratio): FEV1 1.1 (95% CI 0.4 to 4.6). In contrast, dose ratios for systemic responses showed that fenoterol was more potent than salbutamol: serum potassium 3.7 (95% CI 2.0 to 6.0), tremor 5.7 (95% CI 1.4 to 10.2), heart rate 1.6 (95% CI 1.0 to 2.3). At a conventional dose of 200 micrograms the only difference in response between the two drugs was observed for tremor (as mean difference): 0.23 log units (95% CI 0.06 to 0.41 log units).

CONCLUSIONS

There was no difference in the bronchodilator potency between fenoterol and salbutamol on a microgram equivalent basis. In contrast, systemic potency was greater with fenoterol, although this difference was not clinically relevant at conventional dosages up to 200 micrograms.

Osmotic release oral drug delivery system of metoprolol in hypertensive asthmatic patients. Pharmacodynamic effects on beta 2-adrenergic receptors

This study investigated the effects of an osmotic release oral drug delivery system of metoprolol on the changes induced by cumulative doses of inhaled salbutamol on bronchomotor tone, skeletal muscle, and the circulatory system after single (day 1) and multiple (day 7) dosing in 18 hypertensive asthmatic patients (forced expiratory volume in 1 second > 50% predicted; diastolic blood pressure > 90 mm Hg). The patients were given 14/190 mg metoprolol, 100 mg atenolol, and placebo once daily for a 7-day period each in a randomized, double-blind, crossover design. At the estimated time of peak plasma concentrations, cumulative doses of salbutamol (12.5, 37.5, 112.5, 412.5, 812.5, and 1612.5 micrograms) were applied every 20 minutes. Specific airway conductance, finger tremor amplitude, heart rate, and blood pressure were registered at baseline and at each dose increment. The slopes of the salbutamol dose-response curves of specific airway conductance did not differ on day 1 (P > .05). On day 7, atenolol caused a shift of the dose-response curves of specific airway conductance to the right (P < .05), whereas metoprolol was indistinguishable from placebo (P > .05). The median cumulative salbutamol concentrations causing a 50% increase in specific airway conductance were 416 and 384 micrograms (days 1 and 7, respectively) for placebo, 594 and 444 micrograms for metoprolol, and 562 and 1419 micrograms for atenolol. The median cumulative salbutamol concentrations causing a 35% increase in tremor were 732 and 706 micrograms for placebo, 812 and 1213 micrograms for metoprolol, and 797 and 1323 micrograms for atenolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Nebuliser performance, pharmacokinetics, airways and systemic effects of salbutamol given via a novel nebuliser delivery system ("Ventstream")

BACKGROUND

Currently available nebulisers are inefficient and show variable aerosol deposition in the lung owing to the differences in the particle size generated. The aim of this study was to compare systemic absorption and bronchodilator effects of salbutamol given via a novel ("Ventstream") and a conventional ("Hudson Updraft II") nebuliser system, having initially evaluated the performance of both nebulisers in vitro. The "Ventstream" nebuliser uses a one way valve system to provide an additional inspiratory side flow to match aerosol delivery with tidal volume.

METHODS

Nebuliser output and particle distribution from 10 Ventstream and 10 Hudson nebulisers were compared in vitro. Eight asthmatic patients, FEV1 55(2)% predicted, were then randomised to receive salbutamol via Ventstream or Hudson nebulisers on separate days. On each day cumulative doses of inhaled salbutamol were given: 1.25 mg, 2.5 mg (1.25 + 1.25 mg), and 5.0 mg (2.5 + 2.5 mg). Airways responses, systemic responses, and plasma salbutamol concentrations were measured at each dose and for up to 240 minutes after the final dose.

RESULTS

The in vitro comparison showed a greater respirable fraction with a higher percentage volume of particles < 5 microns in diameter using Ventstream than Hudson nebulisers (mean (95% CI) for difference): 25.4% (95% CI 22.4% to 28.3%), and a higher aerosol rate of output: 0.08 g/min (95% CI 0.05 to 0.11 g/min). At the 5.0 mg dose the Ventstream produced a twofold greater concentration of plasma salbutamol than the Hudson nebuliser (AUC0-240): 392.1 ng/ml.min (95% CI 240.6 to 543.6 ng/ml.min). There was a higher AUC0-240 for PEFR with the Ventstream than with the Hudson nebuliser: 74.161 x 10(2) (95% CI 39.50 to 108.821 x 10(2). For FEV1 and FEV25-75 there was a difference in the peak response between the 5.0 mg and 2.5 mg doses with the Ventstream only. Extrapulmonary beta 2 responses were greater with the Ventstream than with the Hudson at 2.5 mg and 5.0 mg doses, although the differences did not appear to be clinically relevant.

CONCLUSIONS

The Ventstream produced a twofold increase in the delivery of salbutamol to the lung compared with the Hudson nebuliser, and there was an associated increase in systemic beta 2 responses with an improvement in some parameters of bronchodilator efficacy. As a consequence of improved delivery with the Ventstream, it may be possible to halve the drug dose to produce similar bronchodilator efficacy at reduced cost. Further studies are required to evaluate the value of the Ventstream for delivery of nebulised antibiotics and corticosteroids.

The effects of lower than conventional doses of oral nadolol on relative beta 1/beta 2-adrenoceptor blockade

1. The aim of the present study was to evaluate the relative beta 1/beta 2 antagonist selectivity of the beta-adrenoceptor blocker nadolol, in lower than conventional clinical doses. 2. Eight normal volunteers received single oral doses of either placebo (PL), nadolol 5 mg (N5), 20 mg (N20) or 80 mg (N80) in a single-blind, randomised crossover design. beta 1-adrenoceptor antagonism was assessed by attenuation of exercise tachycardia, and beta 2-adrenoceptor blockade by effects on salbutamol-induced chronotropic, hypokalaemic and finger tremor responses. The relative percentage attenuation of beta 2 and beta 1-mediated responses was calculated and expressed as beta 2:beta 1 selectivity ratios. 3. Nadolol produced dose-related reductions in exercise tachycardia in keeping with increasing beta 1-adrenoceptor blockade; mean % reduction (95% CI) compared with placebo: N5 10.7 (6.6 to 14.8), N20 21.4 (17.3 to 25.4), N80 38.9 (34.8 to 42.9). However, even the lowest dose of nadolol (5 mg) produced almost complete blunting of beta 2-mediated effects and significantly increase exercise hyperkalaemia; peak exercise hyperkalaemia (mmol l-1) (means and 95% CI): PL 4.88 (4.68 to 5.07), N5 5.36 (5.17 to 5.55), N20 5.48 (5.28 to 5.67), N80 5.42 (5.22 to 5.61). beta 2:beta 1 selectivity ratios significantly increased as the dose of nadolol was reduced. 4. These data suggest that whereas in the clinical dose range nadolol behaves as a non-selective beta-adrenoceptor antagonist, as the dose is reduced this drug demonstrates an increasing degree of selectivity for the beta 2-adrenoceptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchodilator subsensitivity after chronic dosing with eformoterol in patients with asthma

PURPOSE

The aim of the present study was to evaluate in vivo and in vitro beta 2-adrenoceptor responsiveness after chronic inhaled therapy with the long-acting beta 2-agonist eformoterol or placebo, given twice daily, in patients with mild to moderate asthma.

PATIENTS AND METHODS

Seven asthmatic patients, age 34 +/- 5 years were evaluated. Mean forced expiratory volume in 1 second (FEV1) (% predicted) at entry was 58 +/- 5%. After at least 2 weeks run-in without beta 2-agonist therapy, patients were randomized to receive regular treatment with eformoterol 24 micrograms twice daily or placebo twice daily given by metered-dose inhaler for 4 weeks, in a double-blind, crossover design. Dose-response curves (DRC) to eformoterol (cumulative dose 6 micrograms to 126 micrograms) for airways and systemic beta 2-responses were constructed at the end of each treatment period. Responses were measured at baseline, 30 minutes after each dose, and for 6 hours after the last dose. In addition, in vitro parameters of lymphocyte beta 2-receptor function were evaluated prior to the DRC after each treatment period.

RESULTS

There was a nonsignificant trend towards higher baseline values after eformoterol compared with placebo for FEV1: 0.16 L (95% CI -0.04 to 0.36) and forced expiratory flow (FEF25-75): 0.27 L/sec (95% CI -0.08 to 0.62). The peak bronchodilator response from the DRC and response 6 hours after the last dose were both significantly (P < 0.05) attenuated after chronic therapy with eformoterol compared with placebo. The mean differences between eformoterol and placebo for delta FEV1 were as follows: peak: 0.26 L (95% CI 0.09 to 0.43), and at 6 hours: 0.39 L (95% CI 0.20 to 0.58). Corresponding values for delta FEF25-75 were as follows: peak: 0.41 L/sec (95% CI 0.10 to 0.71), 6 hours 0.52 L/sec (95% CI 0.22 to 0.82). Systemic responses were likewise significantly blunted after eformoterol treatment compared with placebo. There was also subsensitivity of lymphocyte beta 2-adrenoceptor function after treatment with eformoterol compared with placebo.

CONCLUSIONS

Our results suggest that chronic therapy with eformoterol produces (1) tachyphylaxis to its bronchodilator response, which was greatest at 6 hours after the last dose, (2) tachyphylaxis of extrapulmonary beta 2-mediated responses, and (3) subsensitivity of in vitro beta 2-adrenoceptor function.

Cardiac effects of the beta 3-adrenoceptor agonist BRL35135 in man

The aim of the present study was to evaluate the cardiac effects of the beta 3-adrenoceptor agonist BRL35135, and determine whether beta 3-receptors are involved in mediating chronotropic or inotropic responses in man. Eight normal males received single oral doses of BRL35135 8 mg (BRL) or the selective beta 2-adrenoceptor agonist salbutamol 8 mg (SAL), after pretreatment with either placebo (PL), bisoprolol 5 mg (B5) as a selective beta 1-adrenoceptor antagonist, or nadolol 20 mg (N20) to block beta 1- and beta 2- but not beta 3-receptors. Both BRL and SAL produced a significant increase in postural finger tremor in keeping with beta 2-adrenoceptor stimulation, and this response was totally abolished by pretreatment with N20. Significant increases in systolic blood pressure and Doppler stroke distance occurred with BRL and SAL which were unaffected by pretreatment with B5 and completely blocked by N20, in keeping with beta 2-mediated effects. BRL and SAL produced significant chronotropic and minute distance responses which were unaffected by beta 1-adrenoceptor blockade. However, whereas N20 blocked these responses to SAL, a small but significant response occurred with BRL in comparison with placebo despite complete blockade of co-existing beta 2-mediated effects. Compared with PL, the mean responses to N20/BRL, and the 95% confidence interval for the differences between the means were 7.4 beats min-1 [3.2 to 11.6] (P = 0.002) for heart rate, and 208.8 cm [38.3 to 379.3] (P = 0.02) for minute distance responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the extrapulmonary beta2-adrenoceptor responses and pharmacokinetics of salbutamol given by standard metered dose-inhaler and modified actuator device

1. Ten healthy subjects were randomised to inhale salbutamol via a standard metered-dose inhaler (MDI), or via a modified metered-dose actuator device (MA). Previously published radiolabelled aerosol data had shown that the MA device produced a lower aerosol velocity, reduced oropharyngeal deposition, but with unchanged pulmonary deposition. 2. Dose-response curves (DRC) were constructed with the following cumulative doses of salbutamol: 200 microg, 600 microg (200 microg + 400 microg), 1400 microg (600microg + 800 microg) ad 2600 microg (1400 + 1200 microg). Dose increments were made every 30 min and measurements of extrapulmonary beta2-adrenoceptor responses were performed 20 min after each dose. In addition, plasma salbutamol concentrations were also measured immediately before and for up to 60 min after the last dose. 3. Baseline values were not significantly different between the two study days for any of the measured parameters. 4. Cmax (ng ml(-1)) for plasma salbutamol (as means and 95% CI for difference between MA and MDI) was: 2.0 (0.3-3.7), P = 0.03. Values for t(max) (min), median and range: MA 5 (5-10) vs MDI 5 (5-10); and AUC 0-60, (ng ml(-1) min, mean and 95% CI for difference between MA and MDI): 69 (-5-143), were not significantly different between the two devices. 5. There was a significant (P < 0.01) left shift in the DRC with the MA device compared with the MDI, for hypokalaemic, finger tremor, chronotropic and electrocardiographic (Twave, Q-Tc) responses to salbutamol. Values for the hypokalaemic response (mmol l(-1)) at 2600 microg were (as change from baseline, means and 95% CI for difference between MA and MDI): 0.23 (0.10-0.36). 6. Thus, the MA device produced greater systemic absorption of salbutamol, and associated extrapulmonary beta2-adrenoceptor responses compared with a standard MDI. These results, therefore, suggest that data from radiolabelled aerosol deposition studies may not predict the systemic absorption of inhaled beta2-adrenoceptor agonists.

Studies on the bronchodilator, tremorogenic, cardiovascular and hypokalaemic effects of fenoterol dry powder in asthma

1. The airway and tremor response and cardiovascular and hypokalaemic effects of single and cumulative doses of fenoterol given by dry powder capsules (DPC) and by metered dose inhaler (MDI) were studied in asthmatics in two randomized, crossover trials. 2. Single doses of fenoterol DPC and MDI (0.2 mg, 0.4 mg), investigated in 24 subjects, produced similar, dose-dependent increases in FEV1. Fenoterol DPC caused less tremor response and less hypokalaemic effects than fenoterol MDI. 3. Cumulative doses of fenoterol DPC and MDI (0.2, 0.6, 1.4, 3.0, 6.2 mg), investigated in 12 subjects, produced a comparable bronchodilatation (mean maximum increase in FEV1 was 0.53 +/- 0.06/0.52 +/- 0.081 for DPC/MDI) and a similar, dose-dependent rise in heart rate (35 +/- 3.81/41 +/- 2.25 beats min(-1)). The rise in tremor and the fall in plasma potassium were smaller after DPC than after MDI. The mean maximum changes were 51.58 +/- 6.41/95.83 +/- 6.75 cm s(-2) for tremor and -0.68 +/- 0.09/-0.96 +/- 0.10 mmol l(-1) for potassium. 4. Our findings may result from a difference in the pharmacokinetics of the dry powder and the aerosol formulation, particularly differences in distribution and absorption. 5. In conclusion, fenoterol DPC used in low therapeutic doses (0.2,0.4 mg), is preferable to the MDI. Fenoterol DPC used as rescue medication in high cumulative doses, do not suggest a greater safety margin than the MDI and the same restrictions should be considered for the fenoterol dry powder formulation as suggested for the MDI.

Selectivity of antagonist and partial agonist activity of celiprolol in normal subjects

1. The aims of this study were to assess the relative beta 1/beta 2 selectivity of the antagonist and partial agonist activity (PAA) of celiprolol in man. 2. Eight normal males received single oral doses of celiprolol 200 mg (C200), 400 mg (C400) and 800 mg (C800); atenolol 50 mg (A50), 100 mg (A100) and 200 mg (A200); nadolol 40 mg (N40) and placebo (PL), administered in a single-blind, randomised crossover design. 3. At rest, in the presence of low levels of circulating adrenaline and noradrenergic tone, a low dose of celiprolol (C200) showed evidence of beta 1-PAA by significant increases in systolic blood pressure and resting heart rate. At higher doses (C400, C800), beta 2-PAA became evident by a significant increase in postural finger tremor, whereas C200 had no effect. 4. In the presence of a beta 1-adrenoceptor agonist, as assessed by reduction of exercise tachycardia, increasing doses of celiprolol produced significantly less beta 1-adrenoceptor blockade compared with atenolol. Furthermore, there was no increase in beta 1-adrenoceptor blockade beyond C400. 5. In the presence of a beta 2-adrenoceptor agonist, as assessed by blunting of terbutaline-induced chronotropic, hypokalaemic and finger tremor responses, celiprolol exhibited less beta 2-adrenoceptor blockade than comparable doses of atenolol used in clinical practice. 6. Exercise hyperkalaemia was blunted significantly by C400 and C800 in comparison with all doses of atenolol and nadolol.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of enalapril and spironolactone on terbutaline-induced hypokalemia

OBJECTIVE

To investigate whether enalapril (E) 10 mg and spironolactone (S) 100 mg attenuate the hypokalemic effect of inhaled terbutaline (T).

DESIGN

Randomized single-blind crossover. Subjects received the following treatment combinations: (a) placebo (P), (b) T alone, (c) T + E, or (d) T + S.

SETTING

University Department of Clinical Pharmacology.

PARTICIPANTS

Twenty healthy volunteers (ten male, ten female) of mean age 22.8 +/- 3.1 years.

MAIN OUTCOME MEASURES

Serum potassium, magnesium, ECG changes (R-R interval, T wave, and QTc interval) for 4 h after terbutaline inhalation.

MAIN RESULTS

Baseline serum potassium levels were higher following prior treatment with E and S; P, 3.78 mmol/L (3.67 to 3.88); T + E, 3.93 mmol-1 (3.82 to 4.03); and T + S, 4.03 mmol/L (3.93 to 4.14) (p less than 0.05). Mean potassium concentrations over 4 h were also higher following prior treatment with E and S; T, 3.58 mmol/L (3.54 to 3.63); T + E, 3.68 mmol/L (3.64 to 3.72) (p less than 0.05); and T + S, 3.73 mmol/L (3.68 to 3.78) (p less than 0.01).

CONCLUSIONS

Enalapril and spironolactone protect against the fall in serum potassium over 4 h by elevating baseline potassium concentration. These potassium-sparing drugs, however, should not be used to prevent the hypokalemic and electrocardiographic sequelae of inhaled beta 2-agonists.

Evaluation of in vivo partial beta 1/beta 2-agonist activity: a dose-ranging study with carteolol

1. The aims of this study were to investigate the partial agonist profile of carteolol and evaluate methodology for differentiating relative beta 1 and beta 2 partial agonist activity (PAA) in vivo. 2. Eight normal subjects received single oral doses of carteolol 10 mg, 30 mg and 60 mg; nadolol 40 mg; pindolol 30 mg and placebo, given in a single-blind, randomised crossover design. 3. beta 1-PAA was demonstrated with carteolol by dose-related increases in resting heart rate and systolic blood pressure, and a plateau in the dose-response curve for attenuation of exercise tachycardia. beta 2-PAA with carteolol was evidenced by a dose-related increase in resting finger tremor and progressive attenuation of exercise-induced hyperkalaemia. beta 2-adrenoceptor antagonism was shown by attenuation of terbutaline induced hypokalaemic, chronotropic and finger tremor responses. 4. Carteolol behaved as a non-selective beta-adrenoceptor antagonist with both beta 1 and beta 2-PAA components. In the standard clinical dose range of 10-30 mg, its in vivo PAA effects were relatively beta 1-selective. Thus at low doses, there appeared to be a dissociation between selectivity of antagonist and partial agonist activity. 5. Attenuation of exercise hyperkalaemia appears to be a novel and sensitive method for the evaluation of beta 2-PAA in vivo.