Dose-response of inhaled drugs in asthma. An update

Effect of Aerosolised Salbutamol Administration on Arterial Potassium Concentration in Anaesthetised Horses

Aerosolized salbutamol has been associated with hypokalemia in horses undergoing colic surgery. The objective of this study was to evaluate the effect of aerosolized salbutamol on arterial potassium concentration ([K +]) in healthy anaesthetized horses undergoing elective surgery. Anesthetic records were reviewed from healthy adult horses undergoing elective surgery over a 3-year period with two complete sets of arterial electrolyte (sodium [Na +], potassium [K +], chloride [Cl -], calcium [Ca 2+]) concentration measurements. Records were excluded if intra-operative electrolyte supplementation, antimicrobial administration or noncrystalloid fluid administration were documented or if salbutamol was administered prior to electrolyte measurement. Sixty records which fulfilled inclusion criteria were divided into two groups depending on whether or not aerosolized salbutamol (2μg kg -1) (to treat hypoxemia) was administered after baseline electrolyte measurement and before the second electrolyte measurement. Aerosolized salbutamol was administered (Group S) in 22 horses and not administered (group NS) in 38 horses. There was a significant reduction in [K +] and [Ca 2+] between baseline and the second electrolyte measurement in both groups (P< .001). The reduction in [K +] between baseline and the second electrolyte measurement was significantly greater in group S (12.3%) compared to group NS (6.9%) (P= .017) and was significantly associated with salbutamol administration (P= .04). The results of this study indicate that monitoring [K +] is important in anaesthetized horses, particularly after aerosolized salbutamol administration.

Agemone mexicana flavanones; apposite inverse agonists of the β2-adrenergic receptor in asthma treatment

Asthma is an inflammatory disease of the airway that poses a major threat to human health. With increase industrialization in the developed and developing countries, the incidence of asthma is on the rise. The β2-adrenergic receptor is an important target in designing anti-asthmatic drugs. The synthetic agonists of the β2-adrenergic receptor used over the years proved effective, but with indispensable side effects, thereby limiting their therapeutic use on a long-term scale. Inverse agonists of this receptor, although initially contraindicated, had been reported to have long-term beneficial effects. Phytochemicals from Agemone mexicana were screened against the human β2-adrenergic receptor in the agonist, inverse agonist, covalent agonist, and the antagonist conformations. Molecular docking of the phyto-constituents showed that the plant constituents bind better to the inverse agonist bound conformation of the protein, and revealed two flavanones; eriodictyol and hesperitin, with lower free energy (ΔG) values and higher affinities to the inverse agonist bound receptor than the co-crystallized ligand. Eriodictyol and hesperitin bind with the glide score of -10.684 and - 9.958 kcal/mol respectively, while the standard compound ICI-118551, binds with glide score of -9.503 kcal/mol. Further interaction profiling at the protein orthosteric site and ADME/Tox screening confirmed the drug-like properties of these compounds.

In vitro and in vivo pharmacological profile of PL-3994, a novel cyclic peptide (Hept-cyclo(Cys-His-Phe-d-Ala-Gly-Arg-d-Nle-Asp-Arg-Ile-Ser-Cys)-Tyr-[Arg mimetic]-NH(2)) natriuretic peptide receptor-A agonist that is resistant to neutral endopeptidase and acts as a bronchodilator

The pharmacological and airways relaxant profiles of PL-3994 (Hept-cyclo(Cys-His-Phe-d-Ala-Gly-Arg-d-Nle-Asp-Arg-Ile-Ser-Cys)-Tyr-[Arg mimetic]-NH(2)), a novel natriuretic peptide receptor-A (NPR-A) agonist, were evaluated. PL-3994, a full agonist, has high affinity for recombinant human (h), dog, or rat NPR-As (K(i)s of 1, 41, and 10 nm, respectively), and produced concentration-dependent cGMP generation in human, dog and rat NPR-As (respective EC(50)s of 2, 3 and 14 nm). PL-3994 has a K(i) of 7 nm for hNPR-C but was without effect on cGMP generation in hNPR-B. PL-3994 (1 μm) was without significant effect against 75 diverse molecular targets. PL-3994 or BNP, a natural NPR ligand, produced concentration-dependent relaxation of pre-contracted guinea-pig trachea (IC(50)s of 42.7 and 10.7 nm, respectively). PL-3994, and also BNP, (0.1 nm-100 μm) elicited a potent, concentration-dependent but small relaxation of pre-contracted human precision-cut lung slices (hPCLS). Intratracheal PL-3994 (1-1000 μg/kg) produced a dose-dependent inhibition of the bronchoconstrictor response evoked by aerosolized methacholine, but was without significant effect on cardiovascular parameters. PL-3994 was resistant to degradation by human neutral endopeptidase (hNEP) (92% remaining after 2 h), whereas the natural ligands, ANP and CNP, were rapidly metabolized (≤1% remaining after 2 h). PL-3994 is a potent, selective NPR agonist, resistant to NEP, with relaxant effects in guinea-pig and human airway smooth muscle systems. PL-3994 has the profile predictive of longer clinical bronchodilator activity than observed previously with ANP, and suggests its potential utility in the treatment of asthma, in addition to being a useful research tool to evaluate NPR biology.

Tremor and β(2)-adrenergic agents: is it a real clinical problem?

Tremor is one of the most characteristic adverse effects following administration of β(2)-adrenergic agonists. It is reported by around 2-4% of patients with asthma taking a regular β(2)-adrenergic agonist and is induced by both short-acting and long-acting agents. Tremor associated with β(2)-adrenergic agonists is dose-related and may occur more commonly with oral dosing. The exact mechanism for tremor induction by β(2)-adrenergic agonists is still unknown, but there is some evidence that β(2)-adrenergic agonists act directly on muscle. An early explanation of the tremor was that β(2)-adrenoceptor stimulation shortens the active state of skeletal muscle, which leads to incomplete fusion and reduced tension of tetanic contractions. More recently, tremor has been correlated closely with hypokalaemia. A possible diverse impact of different modes of administration of β(2)-adrenergic agonists on tremorogenic responses has been suggested but solid evidence is still lacking. In any case, the desensitization of β(2)-adrenoceptors that occurs during the first few days of regular use of a β(2)-adrenergic agonist accounts for the commonly observed resolution of tremor after the first few doses. Therefore, tremor is not a really important adverse effect in patients under regular treatment with a β(2)-adrenergic agonist.

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.

Use of short-acting beta2-agonists during pregnancy and the risk of pregnancy-induced hypertension

BACKGROUND

The effect of inhaled short-acting beta(2)-agonists (SABAs) on pregnancy outcome, especially hypertensive complications, is not well documented. After the finding of a possible protective association of inhaled SABAs with pregnancy-induced hypertension (PIH) in a previous study, we decided to further investigate their effect on this condition.

OBJECTIVE

We sought to determine the effect of inhaled SABA use during pregnancy on the risk of PIH (gestational hypertension, preeclampsia, or eclampsia) in asthmatic women.

METHODS

Three of Quebec's administrative databases were linked to constitute a cohort of asthmatic women who had at least 1 delivery between 1990 and 2000. A nested case-control study was performed using up to 10 control subjects matched to each case patient for the year of conception and gestational age. Statistical analyses considered 22 confounders.

RESULTS

The cohort was composed of 3505 asthmatic women who had a total of 4593 pregnancies. Three hundred two patients with PIH and 3013 control subjects were identified. Compared with nonuse, inhaled SABA use during pregnancy was significantly associated with a reduced risk of PIH (adjusted rate ratios: >0-3 doses/week, 0.62 (95% CI, 0.44-0.87); > 3-10 doses/week, 0.51 (95% CI, 0.34-0.79); and >10 doses/week, 0.48 (95% CI, 0.30-0.75)).

CONCLUSIONS

To our knowledge, this is the first study reporting that inhaled SABA use during pregnancy is associated with a reduced risk of PIH. Potential explanations include pharmacologic and physiological effects or residual confounding.

CLINICAL IMPLICATIONS

These results increase the evidence about the safety of inhaled SABAs in this population, although they should not undervalue the importance of maintaining good control of asthma symptoms.

Aerosol delivery devices and obstructive airway disease

Two obstructive lung diseases, asthma and chronic obstructive pulmonary disease, account for the vast majority of prescriptions for aerosolized medications and devices . Asthma is an immunologically mediated condition characterized by episodic reversible airway obstructions that occur in all age groups. In contrast, chronic obstructive pulmonary disease is a condition characterized by relatively irreversible obstruction that is seen in middle-aged and elderly cigarette smokers. Nevertheless, there is sufficient overlap in terms of airway physiology and therapeutics to allow a review of the challenge of aerosol delivery in both conditions in the same article. This review will concentrate on issues related to aerosol delivery.

Co-administration of salbutamol and fluticasone for emergency treatment of children with moderate acute asthma

This study aimed to compare the efficacy of nebulized therapy with salbutamol alone or in combination with fluticasone. In a randomized, double-blind clinical trial, 150 children with moderate acute asthma were randomly assigned to receive by nebulizations either (i) three doses of salbutamol 30 microl/kg per dose, each dose administered every 15 min, (ii) three doses of salbutamol plus two doses of fluticasone 500 microg/dose at 15 and 30 min after first dose of salbutamol, or (iii) three doses of salbutamol/fluticasone 500 microg/dose, each combined dose administered every 15 min. Pulse oxymetry (SaO2), peak expiratory flow (PEF) and Wood et al. (Am J Dis Child, 123, 1972, 123) clinical scale were evaluated at baseline, 15, 30, 45, 60, 90 and 120 min after the first nebulization. Patients in the three groups significantly improved since 15 min after the first nebulization. We did not observe differences in the recovery of SaO2 and PEF among the three groups of treatment (p > 0.10). In group 3, children showed better clinical response at 120 min than the other two groups (p < 0.05). No significant adverse effects were observed with any treatment. To summarize, in children with acute moderate asthma, nebulized salbutamol at an accumulated dose of 90 mul/kg plus fluticasone at an accumulated dose of 1500 microg produced better clinical relief after 2 h. However, similar PEF and SaO2 responses were observed with salbutamol alone or in combination with different doses of fluticasone.

Formoterol delivered via a new multi-dose dry powder inhaler (Certihaler) is as effective and well tolerated as the formoterol dry powder inhaler (Aerolizer) in children with persistent asthma

The Certihaler is a new multi-dose dry powder inhaler for the delivery of formoterol (Foradil), a long-acting beta(2)-agonist. This dose-ranging study compared the efficacy and safety of formoterol 5, 10, 15 and 30 microg and placebo administered via the Certihaler or formoterol 12 microg via a single-dose dry powder inhaler (Aerolizer) in children with persistent asthma. This was a randomized, placebo-controlled, double-blind, double-dummy, incomplete block crossover, dose-finding and pharmacokinetic study. Children (5-12 years, n = 77) received four of the active treatments twice weekly (BID) for 1 week separated by 1-week single-blind washouts. The primary efficacy variable was 12-h AUC of FEV(1) after 1 week's treatment. Secondary variables included serial 12-h FEV(1). A subset of patients (n = 37) participated in a pharmacokinetic analysis. All formoterol doses resulted in significant increases in 12-h AUC of FEV(1) compared with placebo, and there was no difference between active treatments. The onset of action of formoterol was <3 min for all active treatments. Doses of formoterol > or =10 microg via the Certihaler increased FEV(1) significantly for up to 12 h compared with placebo. The 5 microcg dose via the Certihaler and 12 microg dose via the Aerolizer had a significant effect up to 8 and 7 h post-dose, respectively. Urinary excretion of formoterol via the Certihaler increased in a dose-proportional manner. All formoterol doses were well tolerated, but some patients experienced tremor at the 15 and 30 microg doses. Despite the lack of significant differences between the active doses in the overall bronchodilation, formoterol 10 microg BID via the Certihaler was the dose that provided the best balance between efficacy and tolerability: its duration of action was sustained over 12 h, contrary to that the lower dose (5 microg BID), whereas its tolerability, especially with regard to tremor, was better than the higher doses (15 and 30 microg BID). Overall, Certihaler 10 microg BID was not significantly different from formoterol 12 microg BID via Aerolizer.

Clinical efficacy of inhaler devices containing beta(2)-agonist bronchodilators in the treatment of asthma: cochrane systematic review and meta-analysis of more than 100 randomized, controlled trials

BACKGROUND

A number of different inhaler devices are available to deliver beta(2)-adrenoceptor agonist (beta(2)-agonist) bronchodilators in asthma. These include hydrofluoroalkane or chlorofluorocarbon (CFC)-free propelled pressurized metered-dose inhalers (pMDIs), many dry powder inhalers and breath-actuated inhalers.

OBJECTIVE

To determine the clinical efficacy of all available hand-held inhaler devices compared with the standard CFC-containing pMDI for the delivery of short-acting beta(2)-agonist bronchodilators in nonacute asthma in both children and adults.

METHODOLOGY

A systematic review and meta-analysis was carried out of all available randomized, controlled trials (RCTs) using the standard pMDI compared with any other hand-held inhaler device, delivering short-acting beta(2)-agonist bronchodilators in patients with stable asthma.

RESULTS

One hundred and eighteen RCTs were included in this review. No clinical differences were found between the standard CFC-containing pMDI and 12 other hand-held inhaler devices for most outcome measures. We found no evidence of clinical differences between studies using either a 1 : 1 (pMDI: another inhaler) or a 2 : 1 dosing ratio.

CONCLUSIONS

In patients with stable asthma, short-acting beta(2)-agonist bronchodilators in standard CFC-pMDIs are as effective as any other hand-held inhaler device; therefore the cheapest available device that the patient is able to use should always be considered. Pharmaceutical companies should in future submit to regulatory authorities clinical outcome data (as opposed to in vitro data) in support of any dosing schedules greater than 1 : 1 when compared with the standard pMDI. Clinical effectiveness studies that use an intention-to-treat analysis and report more patient-centered outcomes are required.

The influence of inhaler selection on efficacy of asthma therapies

Many different devices are available to aid inhalational drug delivery. Although each device is claimed to have advantages over its rivals, the evidence to support greater efficacy of a particular device is scanty. Most comparative studies are underpowered or flawed in their design. They may use inappropriate end-points, or involve healthy subjects, whose response may be very different from the patient with acute severe asthma. The dosage of drug used in a trial may be at the shallow part of the dose-response curve, masking differences in devices. Only in a few cases have clinical trials detected a significant difference between devices, and trials have rarely taken patient preference into account. The most efficacious device in practice is likely to be the one that the patient will use regularly and in accordance with a health care workers' recommendations.

Optimizing delivery of inhaled corticosteroids: matching drugs with devices

Over the past decade, the therapeutic options for delivering inhaled corticosteroids have greatly increased as newer compounds, formulations, and delivery systems have been developed. In the present article, some of the controversies surrounding inhaled steroid delivery systems will be reviewed, concentrating on differences in systemic bioavailability and emphasizing the need to match delivery systems with particular drugs and target populations. The strategies employed to minimize systemic exposure due to absorption of steroid from the gastrointestinal tract include increasing the first pass metabolism of the drug, the use of holding chambers with pressurized metered dose inhalers, and reformulation to create smaller, more respirable, particles. However, because the drugs and devices are not interchangeable, comparisons of the devices based on clinical studies will be confounded by differences in the pharmacology and pharmacokinetics of the drugs. In addition to the interaction of drugs and devices, the needs of different patient populations should influence design of delivery systems. For example, patients without airflow obstruction may have greater systemic exposure compared to those with obstruction, while young children need different delivery systems from adults. In conclusion, no delivery system can be considered to be intrinsically superior to all others. The delivery system should be judged instead by its ability to optimize the pharmacokinetic properties of the drug, most notably oral bioavailability, and by its suitability for the target subpopulation of asthmatics.

Formoterol provides long-lasting protection against exercise-induced bronchospasm

BACKGROUND

Patients with exercise-induced bronchospasm (EIB) may benefit from a prophylactic beta2-adrenergic agonist that combines rapid onset with long duration of action.

OBJECTIVE

To compare the protective effect against EIB of a single inhaled dose of formoterol powder delivered via the Aerolizer inhaler (Novartis Pharmaceuticals, East Hanover, NJ) with the effect of placebo and albuterol.

METHODS

Eighteen patients with EIB were randomized to treatment in a double-blind, placebo-controlled, four-way, crossover study. Seventeen patients completed all four crossover periods. Each patient received in random sequence a single dose of formoterol (12 or 24 microg), albuterol (180 microg), or placebo at intervals of 5 +/- 2 days. Pulmonary function measurements were taken before and after exercise challenge tests (ECTs) at 15 minutes postdosing and at 4, 8, and 12 hours postdosing.

RESULTS

Both doses of formoterol produced significantly greater protection against EIB, compared with placebo, at all timepoints (P < or = 0.016). The two doses of formoterol were not significantly different from one another at any time. Protection against EIB with albuterol was clinically significant only for the 15-minute ECT and was statistically superior to placebo for the 15-minute and 4-hour ECTs. Although formoterol and albuterol exhibited a rapid onset of action, formoterol provided longer-lasting protection over the 12-hour observation period. Rescue medication was used substantially less with either dose of formoterol, compared with albuterol or placebo. All treatments were well tolerated. Two-hour postdosing electrocardiograms and vital signs were unremarkable for all study treatments.

CONCLUSION

A single dose of formoterol (12 or 24 microg) provides protection against EIB within 15 minutes of dosing and persists for up to 12 hours. Formoterol is safe and well tolerated.

Circadian rhythm of serum cortisol after repeated inhalation of the new topical steroid ciclesonide

The new inhalative glucocorticoid ciclesonide which is activated in lung to a more potent metabolite was hypothesized to have low risk for systemic and local side-effects in man. Therefore, a placebo-controlled, randomized, double-blind, four-period, change-over equivalence study in 12 healthy male volunteers (age 21-28 yr, body weight 62-90 kg) was conducted to assess the influence of three dosage regimens (800 microg in the morning, 800 microg in the evening, 400 microg twice daily for 7 d, metered inhalers) on the circadian time serum cortisol rhythm.

RESULTS

Serum cortisol showed the typical circadian rhythm. The geometric mean of the 24-h mesor (AUC((0-24 h))/24 h) was 7.22 microg/dl for placebo, 6.75 microg/dl for the 800 microg ciclesonide morning dose, 7.08 microg/dl for the 800 microg evening dose, and 6.75 microg/dl for 400 microg ciclesonide inhaled twice daily. Because there was also no influence on cortisol amplitude and acrophase (time of maximum), the profiles after ciclesonide were equivalent to the placebo control. The small differences were considered not to be of clinical significance. In conclusion, inhaled ciclesonide in daily doses of 800 microg for 7 d is without clinically relevant effects on the hypothalamic-pituitary-adrenal axis independent of the time of administration.

Clinical pharmacokinetics of salmeterol

Salmeterol is an inhaled long-acting selective beta(2)-adrenoceptor agonist that is commercially available as the xinafoate (1-hydroxy-2-naphthoic acid) salt of the racemic mixture of the two optical isomers, (R)- and (S)-, of salmeterol. It acts locally in the lung through action on beta2 receptors. Limited data have been published on the pharmacokinetics of salmeterol. Moreover, there are no data on the extent to which inhaled salmeterol undergoes first-pass metabolism. This lack of information is most likely due to the very low plasma concentrations reached after inhalation of therapeutic doses of salmeterol and the problems in developing an analytical method that is sensitive enough to determine these concentrations. When salmeterol is inhaled, plasma concentrations of the drug often cannot be detected, even at 30 minutes after administration of therapeutic doses. Larger inhaled doses give approximately proportionally increased blood concentrations. Plasma salmeterol concentrations of 0.1 to 0.2 and 1 to 2 microg/L have been attained in healthy volunteers about 5 to 15 minutes after inhalation of a single dose of 50 and 400 microg, respectively. In patients who inhaled salmeterol 50microg twice daily for 10 months, a second peak concentration of 0.07 to 0.2 microg/L occurred 45 to 90 minutes after inhalation, probably because of the gastrointestinal absorption of the swallowed drug. Salmeterol xinafoate dissociates in solution to salmeterol and 1-hydroxy-2-naphthoic acid. These two compounds are then absorbed, distributed, metabolised and excreted independently. The xinafoate moiety has no apparent pharmacological activity, is highly protein bound (>99%), largely to albumin, and has a long elimination half-life of about 12 to 15 days in healthy individuals. For this reason, it accumulates in plasma during repeated administration, with steady-state concentrations reaching about 80 to 90 microg/L in patients treated with salmeterol 50microg twice daily for several months. The cytochrome P450 (CYP) isoform 3A4 is responsible for aliphatic oxidation of salmeterol base, which is extensively metabolised by hydroxylation with the major metabolite being alpha-hydroxysalmeterol, with subsequent elimination predominantly in the faeces. It has been demonstrated that 57.4% of administered radioactivity is recovered in the faeces and 23% in the urine; most is recovered between 24 and 72 hours after administration. Unchanged salmeterol accounts for <5% of the excreted dose in the urine. Since the therapeutic dose of salmeterol is very low, it is unlikely that any clinically relevant interactions will be observed as a consequence of the coadministration of salmeterol and other drugs, such as fluticasone propionate, that are metabolised by CYP3A. All the available data clearly show that at the recommended doses of salmeterol, systemic concentrations are low or even undetectable. This is an important point, because it has been demonstrated that the systemic effects of salmeterol are more likely to occur with higher doses, which lead to approximately proportionally increased blood concentrations.

Seretide for obstructive lung disease

Seretide (Advair [North America], GlaxoSmithKline) is an inhaler combination formulation intended for the maintenance therapy of obstructive airways disease. Seretide was developed and made available initially as three multi-dose, dry powder inhaler formulations delivering 50 microg/puff of the long acting beta(2) agonist salmeterol and either 100, 250 or 500 microg/puff of the inhaled corticosteroid fluticasone propionate. In addition to the initial multi-dose dry powder inhaler system (Diskus or Accuhaler), a chlorofluorocarbon (CFC)-free pressurised aerosol formulation has become available. Studied mostly extensively as a maintenance therapy for patients with persistent asthma, the combination inhaler is at least equivalent to its components administered separately and is superior to monotherapy with salmeterol or inhaled corticosteroid in both paediatric and adult populations. The combination has a logical role in the treatment of moderate-to-severe asthma, offering the advantage of increased convenience and possibly improved compliance. In addition to improvements in lung function, symptom scores and quality of life, the combination therapy reduces exacerbation rates, an outcome that contributes to favourable cost-effectiveness. A role as initial maintenance therapy in all forms of persistent asthma is also plausible but there are fewer data concerning the impact of Seretide in milder forms of persistent asthma. Clinical trials are underway to examine the potential role of Seretide in patients with chronic obstructive pulmonary disease (COPD). Salmeterol has been shown to be an effective first-line bronchodilator in COPD and fluticasone has been shown to reduce the frequency and or severity of exacerbations in COPD patients in two key trials. At a time when the prevalence of both asthma and COPD is increasing, Seretide is a valuable step in the management of these common obstructive lung diseases.

Bronchodilating effect of oxitropium bromide in heart disease patients with exacerbations of COPD: double-blind, randomized, controlled study

Anti-cholinergic agents are considered the bronchodilator therapy of first-choice in the treatment of patients with stable chronic obstructive pulmonary disease (COPD) associated with heart disease since they may be as effective or more effective than inhaled beta2-agonists and, moreover, they do not interact with cardiac beta-adrenoceptors. The aim of our study was to evaluate the bronchodilator activity of oxitropium bromide in outpatients suffering from exacerbations of COPD associated with heart diseases (ischaemic heart disease and/or arrhythmias). We recruited 50 consecutive outpatients (33 males and 17 females, mean age 68.6 years, 15 current smokers and 35 ex-smokers). Each patient performed body plethismography in basal condition and 30 min after inhalation of 200 microg metered dose inhaler (MDI) oxitropium bromide administered by a device (Fluspacer). FEV1, FVC, MMEF25-75, sRaw and tRaw were evaluated. Thirty minutes after 200 microg oxitropium bromide administration, we observed a significant improvement in FEV1 11.6% +/- 1 (mean +/- SEM) (P<0.01); FVC, MMEF25-75 sRaw variation was respectively: 9.2% +/- 0.6, 31.4 +/- 2.9, -19.9 +/- 1.1. Placebo did not significantly change pulmonary function. Our data suggest that oxitropium bromide bronchodilator activity is effective in exacerbations of COPD.

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.

The therapeutic ratio of R-albuterol is comparable with that of RS-albuterol in asthmatic patients

BACKGROUND

It has been suggested that R-albuterol produces bronchodilation that is comparable with that of racemic albuterol (RS-albuterol) on a 4:1 dose-for-dose basis but systemic side effects on a 2:1 basis, implying better therapeutic ratio for R-albuterol.

OBJECTIVE

We sought to carefully compare the bronchodilating and systemic effects of R- and RS-albuterol by using a crossover study design.

METHODS

Twenty asthmatic patients (15.1%-28.7% FEV(1) reversibility) were given R-albuterol (6.25-1600 microg), S-albuterol (6.25-1600 microg), RS-albuterol (12.5-3200 microg), or placebo in a crossover, double-blind, placebo-controlled fashion. Cumulative doses were given with a Mefar dosimeter, and FEV(1), heart rate, and plasma K(+) levels were measured 20 minutes after each dose.

RESULTS

Both R- and RS-albuterol produced dose-related improvement in FEV(1) and, at higher doses, increased heart rate and decreased plasma K(+) levels. Neither placebo nor S-albuterol had any significant effect. Individual estimates of the potency ratio for R-albuterol/RS-albuterol were calculated and summarized across all subjects. The geometric mean potency ratio for effects on FEV(1) was 1.9 (95% CI, 1.3-2.8), on HR of 1.9 (95% CI, 1.3-2.9), and on K(+) level of 1.7 (95% CI, 1.3-2.1).

CONCLUSION

All pharmacologic effects of RS-albuterol reside with the R-enantiomer, and S-albuterol is clinically inactive. The R-albuterol/RS-albuterol potency ratios for local (FEV(1)) and systemic effects (heart rate and K(+)) are similar, suggesting a comparable therapeutic ratio for R-albuterol and RS-albuterol in asthmatic subjects.

Suppression of hypothalamic-pituitary-adrenal axis activity with inhaled flunisolide and fluticasone propionate in adult asthma patients

BACKGROUND

Suppression of the hypothalamic-pituitary-adrenal (HPA) axis, a potential systemic effect of inhaled corticosteroid therapy, can be quantified by monitoring serum, urinary, and salivary cortisol levels.

OBJECTIVES

1) Compare the effects on HPA axis of the inhaled corticosteroids flunisolide and fluticasone propionate versus placebo and oral prednisone. 2) Estimate dose-potency ratio for HPA-axis suppression.

METHODS

Multicenter, randomized, placebo-controlled, open-label, 21-day trial. Active regimens were flunisolide 500 and 1,000 microg, twice daily; fluticasone propionate 110, 220, 330, and 440 microg, twice daily; and prednisone, 7.5 mg daily. Enrolled patients were nonsmokers, 18 to 50 years of age, with persistent mild-to-moderate asthma and had not used oral, nasal, or inhaled corticosteroids for 6 months before study. Main outcome measures were area under serum cortisol concentration curve for 22 hours (AUC(0-22h)); 24-hour urinary cortisol level; and 8 AM salivary cortisol level.

RESULTS

One hundred fifty-three patients were randomly assigned to active treatment or placebo; 125 patients completed the study and were at least 80% compliant with their regimens. Both fluticasone propionate and flunisolide caused dose-dependent suppression of HPA axis, which was statistically greater for fluticasone propionate (P = 0.0003). Dose-potency ratio showed 4.4 times more serum-cortisol suppression/microgram increase in dose with fluticasone propionate than with flunisolide. Diurnal pattern of serum cortisol suppression was persistent with fluticasone propionate and "remitting" with flunisolide. Salivary and urinary cortisol data were qualitatively similar to serum cortisol results.

CONCLUSIONS

Fluticasone caused significantly more suppression of HPA axis than flunisolide. Flunisolide may provide a safe option for patients with asthma requiring long-term inhaled corticosteroid therapy.

Asthma stability after oral prednisone: a clinical model for comparing inhaled steroid potency

Clinical studies comparing the potency of inhaled corticosteroids require steep dose-response slopes (b) and minimal response variability (s), as statistical power is inversely related to the s/b ratio. To evaluate a new study model, we performed a randomized, crossover study of 12 adult asthmatics who required 800 to 2,000 microg of inhaled corticosteroids daily, and calculated s/b for 21 raw clinical outcomes and 36 mathematically derived variables based on these raw outcomes. Each of two 21-d treatment periods was preceded by 4 to 7 d of oral prednisone to maximize asthma control and minimize carry-over of previous inhaled treatment. Treatments were 100 and 800 micron/d of an HFA-134a beclomethasone dipropionate formulation. Assessments included daily home spirometry, histamine challenge, inhaled albuterol use, and asthma symptom scores. Efficacy variables with the greatest power (lowest s/b values) were A.M.FEF25-75, A.M.FEV1, and A.M.PEF, (s/b = 0.46, 0.48, and 0.59). Carry-over between treatment periods was not significant. Crossover study sample size calculations using these ratios yielded samples of 23, 25, and 37 patients, respectively. Otherwise identical parallel studies would require sample sizes of 657, 1,438, and 2,261 patients. These results support the use of a crossover asthma stability model after a short course of oral prednisone as a clinical study model for comparing topical potency of inhaled corticosteroids.

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.

Comparative in vivo lung delivery of hydrofluoroalkane-salbutamol formulation via metered-dose inhaler alone, with plastic spacer, or with cardboard tube

STUDY OBJECTIVE

To compare the lung delivery of chlorofluorocarbon-free salbutamol via a pressurized metered-dose inhaler (pMDI) alone, a pMDI with a small-volume plastic spacer, and a pMDI with a cardboard tube.

DESIGN

A randomized, single (investigator)-blind, three-way, crossover study.

SETTING

The Asthma and Allergy Research Group, Ninewells Hospital, University of Dundee, Dundee, Scotland, UK.

PARTICIPANTS

Twelve healthy volunteers aged 16 to 65 years.

INTERVENTIONS

The subjects were administered 400 microg of salbutamol via a pMDI alone, via a pMDI plus a small-volume plastic spacer, or via a pMDI plus a cardboard tube.

MEASUREMENTS AND RESULTS

Blood samples for plasma salbutamol concentrations were taken at 5 min, 10 min, and 20 min after inhalation, to measure lung bioavailability as a surrogate for relative lung dose. The addition of the plastic spacer resulted in a significantly higher maximal plasma salbutamol concentration (CMAX) and average plasma salbutamol concentration (CAV) than the pMDI used alone. This amounted to a 1.48-fold (32%) difference (95% confidence interval [CI], 1.03 to 2.13) for CMAX and a 1.42-fold (30%) difference (95% CI, 1.01 to 2.00) for CAV. There was no significant difference in the CMAX or CAV comparing the addition of the cardboard tube with the plastic spacer or the pMDI alone.

CONCLUSIONS

Using a chlorofluorocarbon-free pMDI with a plastic spacer produced statistically, but not biologically, significant greater lung delivery of salbutamol. If a spacer is required for reasons other than increasing delivered drug dose, then the addition of a readily available cardboard tube will fulfill many of the required functions with no expense to the patient.

A randomized, 12-week, double-blind, placebo-controlled study comparing formoterol dry powder inhaler with albuterol metered-dose inhaler

BACKGROUND

Formoterol is a beta2-adrenergic agent which, when inhaled, produces rapid and long-lasting bronchodilatation.

OBJECTIVE

The aim of this study was to compare the efficacy, safety, and tolerability of formoterol powder for inhalation delivered via the Aerolizer device with placebo and with albuterol delivered via metered-dose inhaler in patients with mild to moderate persistent asthma.

METHODS

In a multicenter, double-blind, parallel-group study, 541 patients were randomized at 26 trial sites to receive either formoterol, 12 microg twice daily; formoterol, 24 microg twice daily; albuterol, 180 microg four times daily; or a placebo for 12 weeks. The effects of each treatment on lung function, asthma symptoms, and frequency of rescue albuterol use were evaluated. Adverse effects and clinical laboratory parameters were also evaluated.

RESULTS

The bronchodilatory effects of formoterol were rapid in onset and persisted for 12 hours. Both formoterol doses were more effective than placebo and albuterol for objective measures of lung function. Morning and evening peak expiratory flow rates were more improved with formoterol, and formoterol provided significantly greater improvements in asthma symptom scores compared with both albuterol and placebo. Overall, patients taking formoterol used significantly less rescue medication than did those taking albuterol or placebo. Nocturnal awakenings occurred less often with formoterol than with placebo or albuterol. The therapeutic effects of formoterol were maintained over the entire 12 weeks of treatment. Adverse events were similar for all treatment groups, and clinical laboratory data were unremarkable.

CONCLUSIONS

Rapid-onset, long-acting formoterol, administered via the Aerolizer inhaler, is an effective and safe treatment for patients with mild to moderate persistent asthma.

Randomized trial of inhaled flunisolide versus placebo among asthmatic patients discharged from the emergency department

STUDY OBJECTIVE

Inhaled corticosteroids (ICs) improve airflow and decrease symptoms in patients with chronic asthma. We examined whether high-dose inhaled flunisolide would have similar benefits after an emergency department visit for acute asthma.

METHODS

Over a 16-month period at one inner-city ED, we documented 551 eligible patients (acute asthma; age 18 to 50 years; no ICs in past week; no oral corticosteroids in past month; and peak expiratory flow rate [PEFR] <70% of predicted value after first beta-agonist treatment); 104 patients agreed to participate. At ED discharge, all patients were given prednisone 40 mg/d for 5 days and inhaled beta-agonists as needed and were randomly assigned to receive high-dose inhaled flunisolide 2 mg/d (n=51) or placebo (n=53). Patients were telephoned daily and asked to return for PEFR measurement at 3, 7, 12, 21, and 24 days.

RESULTS

Despite precautions, 28% (16 receiving flunisolide and 13 receiving placebo) of patients were completely lost to follow-up, 2 patients had only one follow-up (day 3), 2 patients receiving flunisolide withdrew because of medication-related bronchospasm, and 4 patients in each group experienced relapse. Among the 63 remaining patients, we found no difference between flunisolide and placebo at day 24 follow-up in percent predicted PEFR (87% versus 83% on day 24, P =.36; difference 4%, 95% confidence interval [CI] -5% to 13%). Nocturnal wheezing and nocturnal albuterol inhaler use was higher among patients receiving flunisolide than those receiving placebo on day 24 (48% versus 18% for nocturnal wheezing, P =.01; mean difference 30%, 95% CI 11% to 49%; 3.8 versus 1.4 nocturnal albuterol puffs, P =.03; mean difference 2.4 puffs, (95% CI 0.2 to 4). Levels of dyspnea, cough, and overall well-being were similar between the flunisolide and placebo groups.

CONCLUSION

Addition of high-dose inhaled flunisolide to standard therapy does not benefit inner-city patients with acute asthma in the first 24 days after ED discharge. Airway inflammation during acute asthma may require higher doses or more potent anti-inflammatory agents.

Challenges in evaluating controller asthma therapy in children

Clinical data about the efficacy and safety of controller medications for pediatric patients of all ages are limited, especially when compared with the amount of data available for medications for adults. The considerable data collected so far in adults about these therapeutic agents need to be confirmed in children because pharmacologic profiles will not necessarily be the same for children. Clinical research studies need to include younger populations so that the necessary information can be available for physicians who want to use controller therapy for their pediatric patients. Special challenges confront the pharmaceutical companies and the research investigators who undertake these clinical studies, but such challenges are surmountable.

Equivalence testing and equivalence limits of metered-dose inhalers and dry powder inhalers measured by in vitro impaction

In this study, criteria for the acceptability of comparative in vitro equivalence testing are proposed. Furthermore, the following equivalence limits for in vitro impaction methods are postulated: the 90% confidence interval (CI) of the in vitro deposition ratio of the test product and the reference product should lie within 0.80-1.20. The aim of this study was to challenge these limits by applying them to in vitro impaction results of several groups of pressurized metered-dose inhalers and dry powder inhalers containing salbutamol and beclomethasone dipropionate. The deposition results were obtained with the Twin Impinger. All products had a marketing authorization in The Netherlands and were considered therapeutically equivalent within each group. The postulated equivalence limits/group were challenged by fictitiously assigning a preparation as a test product or reference product and calculating the 90% CI of the deposition ratio of the test and reference products. All possible combinations of products within a group were tested. The products were considered equivalent if the 90% CI of the quotient lay within 0.80-1.20. In most cases, the quotient of the test product and reference product remains within 0.80-1.20, but due to a high variability in the deposition results of several products, the 90% CI of the quotient sometimes falls outside the proposed equivalence limits. It is concluded that the equivalence limits postulated are rather conservative, with respect to accepting equivalence. The limits can therefore serve as a prudent predictor of equivalence within the acceptability criteria proposed, but have to be further validated.

Comparable effects of inhaled fluticasone propionate and budesonide on the HPA-axis in adult asthmatic patients

This randomized, double-blind, double-dummy, multicentre cross-over study compared the effects on the hypothalamic-pituitary-adrenal (HPA) axis of fluticasone propionate (750 microg twice daily given via the Diskus) and budesonide (800 microg twice daily given via the Turbuhaler). Two treatment periods of 2 weeks each were preceded by a 2-week run-in period and separated by a 2-week washout period. During run-in and washout, patients received beclomethasone dipropionate (BDP) or budesonide at a constant dose of 1500-1600 microg day(-1). Sixty patients aged 18-75 years with moderate to severe asthma not fully controlled by treatment with 1500-1600 microg day(-1) budesonide or BDP entered run-in and 45 completed the study. HPA axis suppression was assessed by morning serum cortisol (area under the curve from 08.00 to 10.30 hours) and 12-h nocturnal urinary cortisol excretion, measured at the end of run-in (baseline 1), at the end of washout (baseline 2), and at the end of each treatment period. Neither budesonide nor fluticasone produced significant suppression of either parameter compared to baselines. Only a few patients had serum-cortisol and urinary cortisol values below the normal range, before and after treatment. This shows that the patients did not have adrenal suppression before entering the study. The ratio between the AUC serum cortisol measured after fluticasone treatment and after budesonide treatment was 0.99 (95% CI 0.92-1.06), indicating equivalent effects on the HPA axis. This result was achieved after having omitted two patients' results, due to their very sensitive reaction to budesonide, but not to fluticasone. Two exacerbations of acute asthma occurred during budesonide treatment and none during fluticasone treatment. Both treatments were well tolerated. In conclusion, budesonide 1600 microg day(-1) via Turbuhaler and fluticasone propionate 1500 microg day(-1) via Diskus had no clinical effects on the HPA axis in patients with moderate to severe asthma.

Measures of hypothalamic-pituitary-adrenal function in patients with asthma treated with inhaled glucocorticoids: clinical and research implications

In asthmatic patients treated with inhaled glucocorticoids there may be a risk of suppression of hypothalamic-pituitary-adrenal (HPA) function. The aim of the present study was to review peer-refereed data on HPA function in asthmatic patients taking inhaled glucocorticoids, and to discuss the value of HPA function measures in clinical practice and research. There is no evidence that inhaled glucocorticoids in recommended doses cause clinically significant HPA insufficiency. If sensitive measures of basal adrenal activity are used, however, dose-related suppressive effects with specific drugs and application systems can be detected. In adults, fluticasone propionate appears to be more potent than budesonide or triamcinolone acetonide in suppressing measures of basal adrenal activity. Measures of basal adrenal activity are useful in clinical trials that assess and compare systemic activity of specific drugs, application devices, and administration regimens, but have no place in the management of asthma.

Inhaled corticosteroids for adult asthma: impact of formulation and delivery device on relative pharmacokinetics, efficacy and safety

Metered dose inhalers (MDIs) are the mainstay of inhaled steroid therapy for asthma. With the phasing out of traditional chlorofluorocarbon (CFC) propellants and their replacement with a new generation of CFC-free products, it is becoming clear that formulation and inhaler characteristics can markedly affect the drug delivery. It now seems necessary to compare inhalers not only on the basis of the properties of the steroid molecules but also to take into account the effect of propellants and other inhaler characteristics. The impact of formulation and delivery device on relative pharmacokinetics, therapeutic efficacy and tolerability is illustrated by a new preparation of beclomethasone dipropionate (BDP) in an inhaler containing hydrofluoroalkane (HFA) propellant, called Qvar (3M Health Care, U.K.). This drug preparation delivers the majority of particles (60%) in the fine particle range. This appears to be associated with improved lung deposition, a halving of dose requirements of BDP, but no evidence of clinically relevant adrenal suppression when used in therapeutic doses. Prescribers need to be aware of the impact of formulation on pharmacokinetics of inhaled steroids in order to offer the lowest effective dose and give clear instructions to patients who are changing to a CFC-free product.

Asthma-related prescribing patterns with four different corticosteroid inhaler devices

Four types of corticosteroid inhaler devices are available in New Zealand for first-line treatment of asthma, including two aerosol systems [Autohaler (3M Healthcare Ltd, Loughborough, U.K.; 3M Pharmaceuticals (Australia Pty Ltd, Sydney, Australia) and MDI (Glaxo Wellcome PLC, Ware, U.K.)] and two dry powder systems [Diskhaler (Glaxo Wellcome) and Turbuhaler (Astra AB, Sodertalje, Sweden)]. Rates of asthma-related health care consumption and treatment outcomes associated with use of the different inhalers are unknown. In this retrospective survey, asthma-related primary health care consultation and prescription patterns were compared in a large general practice population for each corticosteroid inhaler device prescribed as first-line treatment. An electronic search of a computerized clinical database yielded the medical records of 5704 patients with physician-diagnosed asthma who were prescribed either the Autohaler, Diskhaler, MDI or Turbuhaler as their sole corticosteroid inhaler device in the previous 12 months. The mean daily inhaled corticosteroid dose was lowest for the Autohaler (569 micrograms day-1; 95% CI: 538-605), followed by the Diskhlaer (638 micrograms day-1; 95% CI: 609-670) and MDI (665 micrograms day-1; 95% CI: 638-673), and was highest for the Turbuhaler (990 micrograms day-1; 95% CI: 954-1029, P < 0.001). A relatively high proportion of patients aged 19-49 years in the Turbuhaler and Diskhaler groups (29% and 23%, respectively) received at least one inhaled corticosteroid prescription including a daily dose greater than 1500 micrograms compared with the MDI group (4%). In the Diskhaler group the mean daily inhaled corticosteroid dose prescribed for adult patients was similar to that for the Turbuhaler group (904 micrograms day-1 and 1058 micrograms day-1, respectively). These data suggest that in New Zealand the dry powder corticosteroid inhaler devices are prescribed for adults at significantly higher doses than the aerosol inhaler devices. Clinical databases of this type yield valuable information on drug utilization in large patient populations and usefully assess clinical prescribing practices.

Comparison of potency of inhaled beclomethasone and budesonide in New Zealand: retrospective study of computerised general practice records

OBJECTIVE

To determine whether inhaled budesonide and beclomethasone are equipotent in the treatment of asthma in primary care.

DESIGN

Retrospective study of computerised clinical records from 28 general practices in New Zealand.

SUBJECTS

5930 patients who received 16 725 prescriptions for inhaled budesonide or beclomethasone from 1 July 1994 to 30 June 1995.

SETTING

General practices on the database of the Royal New Zealand College of General Practitioners Research Unit. Linked information from secondary care was available for a subset of the practices.

MAIN OUTCOME MEASURE

Mean prescribed daily inhaled corticosteroid dose.

RESULTS

The daily prescribed dose was higher for patients receiving inhaled budesonide (mean 979 microg) than beclomethasone (mean 635 microg), a difference of 344 microg (95% confidence interval 313 to 376 microg). This difference was consistent in all age bands and with different types of inhalation device. Evidence of systematic prescribing of higher doses of budesonide to patients with more severe asthma was not found.

CONCLUSIONS

In primary care in New Zealand evidence suggests that budesonide is less potent than beclomethasone. Consideration of validated, established, and other possible markers of asthma severity did not support confounding by severity as a reason for the higher prescribed doses of budesonide. Pending further epidemiological evaluation, international asthma guidelines may need to be modified on the equivalence of inhaled corticosteroid doses. Furthermore, the comparative potency of newly developed inhaled steroids in clinical trials will need to be confirmed in appropriately designed epidemiological studies based in general practice.

Safety of hydrofluoroalkane-134a beclomethasone dipropionate extrafine aerosol

Herein we assess the safety of an inhaled formulation of beclomethasone dipropionate (BDP) which uses the propellant hydrofluoroalkane-134a (HFA) for the treatment of asthma. Acute local tolerability (as assessed by the incidence of cough and mean forced expiratory volume after 1 s inhalation) was similar for both BDP and placebo formulated in either chlorofluorocarbon (CFC) or HFA propellants. A total of 43 patients were treated with HFA-BDP (0, 200, 400 or 800 micrograms day-1) or CFC-BDP (800 micrograms day-1) for 14 days and their 24 h urinary free cortisol (UFC) excretion and response to cosyntropin stimulation were measured. There was no difference in UFC between any of the doses of HFA-BDP and CFC-BDP. Adrenal responsiveness to cosyntropin stimulation was normal in all but one patient. Two large 12 week phase III trials compared HFA-placebo, HFA-BDP 400 micrograms day-1 and CFC-BDP 800 micrograms day-1 (n = 347), and HFA-BDP 800 micrograms day-1 and CFC-BDP 1500 micrograms day-1 (n = 233). For HFA-BDP at either dose, CFC-BDP 800 micrograms day-1 and HFA-placebo, the number of patients with morning plasma cortisol concentrations below normal was less than 4.4% but was 14.6% for CFC-BDP 1500 micrograms day-1. The incidence of adverse events was lower in the HFA-BDP groups than in the CFC-BDP groups (P = 0.012). The data indicate that, at doses of up to 800 micrograms day-1, HFA-BDP is at least as well tolerated as CFC-BDP. Other studies have found that equivalent efficacy is reached at lower doses of HFA-BDP than CFC-BDP. Equivalent efficacy at a lower dose and equivalent safety at the same dose imply that HFA-BDP may have a more favourable risk: benefit ratio than CFC-BDP when used at the recommended lower doses.

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.