Beta-adrenergic agonists for acute, severe asthma

Comparison of spray congealing and melt emulsification methods for the incorporation of the water-soluble salbutamol sulphate in lipid microparticles

CONTEXT

Salbutamol sulphate is widely used as bronchodilator for the treatment of asthma. Its use is limited by the relatively short duration of action and hence sustained delivery of salbutamol sulphate offers potential benefits to patients.

OBJECTIVE

This study explores the preparation of lipid microparticles (LMs) as biocompatible carrier for the prolonged release of salbutamol sulphate.

MATERIALS AND METHODS

The LMs were produced using different lipidic materials and surfactants, by classical melt emulsification-based methods (oil-in-water and water-in-oil-in-water emulsions) and the spray congealing technique.

RESULTS

For the LMs obtained by melt emulsification a lack of release modulation was observed. On the other hand, the sustained release of salbutamol sulphate was achieved with glyceryl behenate microparticles prepared by spray congealing. These LMs were characterized by scanning electron microscopy, X-ray diffractometry and differential scanning calorimetry. The drug loading was 4.72% (w/w). The particle size distribution measured by laser diffraction and electrical zone sensing was represented by a volume median diameter (Dv(50)) of 51.7-71.4 µm. Increasing the atomization air pressure from 4 to 8 bar produced a decrease of the Dv(50) to 12.7-17.5 µm.

CONCLUSIONS

Incorporation of the hydrophilic salbutamol sulphate into LMs with sustained release characteristics was achieved by spray congealing.

Liposomes prolong the therapeutic effect of anti-asthmatic medication via pulmonary delivery

Purpose

The main objective of this study was to develop a novel aerosolized liposome formulation for pulmonary delivery of anti-asthmatic medication and to explore the relationship between the bioavailability and anti-asthmatic efficacy of such a formulation. Asthma treatment usually requires frequent administration of medication for sustained bronchodilating response. Liposomes are known for their capability for sustained drug release and thus would be a suitable delivery system for anti-asthmatic medication for prolonged therapeutic effect. Salbutamol sulfate (SBS) was chosen as the model drug in this study because of its high water solubility and fast absorption after administration.

Methods

SBS was efficiently encapsulated into liposomes by the vesicular phospholipid gel technique. SBS permeability across the pulmonary membrane of an Asian toad was determined by in vitro study. Intratracheal administration of liposomes labeled with the fluorescent dye 1,1′-dioctadecyltetramethyl indotricarbocyanine iodide (DiR) in a rat model was assessed by a small animal imaging system and pharmacokinetic analysis. Pharmacodynamic analysis was performed in guinea pigs using the Konzett–Rössler method.

Results

SBS was efficiently encapsulated into liposomes with encapsulation efficiency as high as 70%. The particle size of the SBS liposome suspension was approximately 57 ± 21 nm. In the in vitro study of permeability across the pulmonary membrane of Asian toads, SBS from liposomes demonstrated a slower transport rate compared to free SBS solution. Pulmonary delivery of liposomes in a rat model showed that the liposomes were effectively distributed in the respiratory tract and lungs, and that the release of SBS from liposomes was sustained for at least 48 hours. Pharmacodynamic analysis in a guinea pig model showed that the anti-asthmatic effect of SBS liposomes persisted for up to 18 hours, whereas that of free SBS solution was less than 8 hours.

Conclusion

The overall results demonstrated that liposomes could increase the concentration and retention time of SBS in the lungs and therefore prolong its therapeutic effect.

Development and characterization of Eudragit based mucoadhesive buccal patches of salbutamol sulfate

For systemic drug delivery, the buccal region offers an attractive route of drug administration. Salbutamol sulfate is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. It's oral bioavailability is ∼40% due to extensive first pass metabolism. Salbutamol sulfate patches were prepared using Eudragit L-100, HPMC, PVA and Carbopol 934 in various proportions and combinations using PEG-400/PG as plasticizers. Patches were laminated on one side with a water impermeable backing layer for unidirectional drug release. The thickness of medicated patches were ranged between 0.23 ± 0.008 and 0.59 ± 0.007 mm and mass varied between 65.23 ± 3.3 and 117.92 ± 4.2 mg. Patches showed an increase in mass and swelling index with PEG-400 when compared with PG. The surface-pH of patches ranged between 6 and 7. Formulations E7 (7.5 mL Eudragit L-100, 15 mL HPMC K4M, 7.5 mL PVA and 2 mL PEG-400), E12 (7.5 mL Eudragit L-100, 7.5 mL PVA, 15 mL Carbopol and 2 mL PEG-400), F7 (7.5 mL Eudragit L-100, 15 mL HPMC K4M, 7.5 mL PVA and 2 mL PG), and F12 (7.5 mL Eudragit L-100, 7.5 mL PVA, 15 mL Carbopol and 2 mL PG) showed high folding endurance. Residence time of the tested patches ranged between 101 and 110 min. The maximum in vitro release was found to be 99.93% over a period of 120 min for formulation F12. Data of in vitro release from patches were fitted to different kinetic models such as Higuchi and Korsmeyer-Peppas models to explain the release profile. Formulations E7 and F7 were best fitted to the non-Fickian, where as formulations E12 and F12 showed Fickian/anomalous drug release. Stability studies indicated that there was no change in the chemical and physical characteristics during the test period.

Transdermal delivery of salbutamol sulphate: formulation and evaluation

Salbutamol patches were prepared and evaluated. The effect of different Eudragits and various plasticizers on the properties of the patches were studied. Patches were prepared by casting method employing different plasticizers. These patches were evaluated for weight, thickness uniformity, swelling index, tensile strength, elongation percent and moisture absorption capacity. Release was studied. Tensile strength of the patches using Eudragit RS 100 as well as RS100 + L100 and triacetin was the lowest. Formulae containing 10% oleic acid and 5% dimethyl formamide, respectively, showed the highest permeability. These two formulae were studied clinically, the first formula only showed a significant improvement.

Population pharmacodynamic model of bronchodilator response to inhaled albuterol in children and adults with asthma

BACKGROUND

Because interpatient variability in bronchodilation from inhaled albuterol is large and clinically important, we characterized the albuterol dose/response relationship by pharmacodynamic modeling and quantified variability.

METHODS

Eighty-one patients with asthma (24% African American [AA]; 8 to 65 years old; baseline FEV1, 40 to 80% of predicted) received 180 microg of albuterol from a metered-dose inhaler (MDI), and then 90 microg every 15 min until maximum improvement or 540 microg was administered; all then received 2.5 mg of nebulized albuterol. FEV1 was measured 15 min after each dose. The population cumulative dose/response data were fitted with a sigmoid maximum effect of albuterol (Emax) [maximum percentage of predicted FEV1 effect] model by nonlinear mixed-effects modeling. The influence of covariates on maximum percentage of predicted FEV1 reached after albuterol administration (Rmax) and cumulative dose of albuterol required to bring about 50% of maximum effect of albuterol (ED50) and differences between AA and white patients were explored.

RESULTS

ED50 was 141 microg, and Emax was 24.0%. Coefficients of variation for ED50 and Emax were 40% and 56%, respectively. Ethnicity was a statistically significant covariate (p < 0.05). AA and white patients reached 82.4% and 91.9% of predicted FEV1, respectively (p = 0.0004); and absolute improvement in percentage of predicted FEV1 was 16.6% in AA patients vs 26.7% in white patients (p < 0.0003). There were no baseline characteristic differences between AA and white patients. Nebulized albuterol increased FEV1 > or = 200 mL in 21% of participants. Heart rate and BP were unchanged from baseline after maximal albuterol doses.

CONCLUSIONS

Our model predicts that 180 microg of albuterol by MDI produces a 14.4% increase in percentage of predicted FEV1 over baseline (11.7% in AA patients, and 17.5% in white patients). Emax varies widely between asthmatic patients. AA patients are less responsive to maximal doses of inhaled albuterol than white patients.

Enhanced transdermal delivery of salbutamol sulfate via ethosomes

The main objective of the present work was to compare the transdermal delivery of salbutamol sulfate (SS), a hydrophilic drug used as a bronchodilator, from ethosomes and classic liposomes containing different cholesterol and dicetylphosphate concentrations. All the systems were characterized for shape, particle size, and entrapment efficiency percentage, by image analysis optical microscopy or transmission electron microscopy, laser diffraction, and ultracentrifugation, respectively. In vitro drug permeation via a synthetic semipermeable membrane or skin from newborn mice was studied in Franz diffusion cells. The selected systems were incorporated into Pluronic F 127 gels and evaluated for both drug permeation and mice skin deposition. In all systems, the presence of spherical-shaped vesicles was predominant. The vesicle size was significantly decreased (P < .05) by decreasing cholesterol concentration and increasing dicetylphosphate and ethanol concentrations. The entrapment efficiency percentage was significantly increased (P < .05) by increasing cholesterol, dicetylphosphate, and ethanol concentrations. In vitro permeation studies of the prepared gels containing the selected vesicles showed that ethosomal systems were much more efficient at delivering SS into mice skin (in terms of quantity and depth) than were liposomes or aqueous or hydroalcoholic solutions.

The use of inhaled formoterol in the treatment of asthma

OBJECTIVE

To discuss the clinical efficacy and safety of formoterol when used to relieve symptoms of asthma and prevent exercise-induced bronchoconstriction (EIB).

DATA SOURCES

A PubMed search was performed for articles published between 1997 and 2005 with the keywords formoterol, asthma, and long-acting beta2-adrenergic agonist, with cross-referencing to identify peer-reviewed journal articles.

STUDY SELECTION

Published articles on the clinical use of formoterol for asthma or EIB were included as well as articles detailing the pharmacologic properties of the drug. To present a thorough review of the literature, published studies based on patient number, study design, or other measures of study quality were not excluded.

RESULTS

Formoterol is the only long-acting beta2-adrenergic agonist that combines a rapid onset of action (within 3 minutes) with a long duration of effect (approximately 12 hours). Clinically, as recommended by asthma treatment guidelines, formoterol in conjunction with inhaled corticosteroids (ICSs) is a preferred treatment for moderate to severe persistent asthma. Significant clinical data support the use of formoterol in combination with ICSs for the treatment of asthma, with studies demonstrating improved pulmonary function and symptom scores and decreased need for maintenance ICSs and short-acting beta2-adrenergic agonists (SABAs) as relief medication. Recent studies also demonstrate that use of formoterol as needed as relief medication is associated with a prolonged time to exacerbation, improved pulmonary function, and decreased asthma symptoms. When used as monotherapy, formoterol provides protection against EIB. Clinical data also demonstrate that formoterol is safe and well tolerated even in high doses, with an adverse event profile similar to that of SABAs.

CONCLUSION

Overall, formoterol is safe and effective as adjunct controller therapy for moderate and severe persistent asthma and as monotherapy for EIB.

Clinical pharmacokinetic and pharmacodynamic evaluation of transdermal drug delivery systems of salbutamol sulfate

Transdermal drug delivery formulation containing 5 mg/patch of salbutamol sulfate (SS), providing an input rate of 100 microg/h of SS was formulated and subjected for pharmacokinetic and pharmacodynamic evaluation in moderately asthmatic patients (n=6). A linear correlation was observed between cumulative amount of drug diffused in vitro and cumulative AUC0-t of serum concentration-time curve (R2=0.99). A steady-state serum concentration of 2.87+/-0.1 ng/ml (per milligram dose) was attained after an initial lag period of 4.67+/-1.03 h. The elimination half-life, clearance rate and elimination rate constant was 3.35+/-1.07 h, 256.12+/-3.55 ml/min and 0.24+/-0.09 h(-1), respectively. The mean forced expiratory volume in one minute (FEV1) of the patients was 2.2+/-0.14l during steady state. The pharmacokinetic results correlated well with the FEV1 response of patients.

Management of acute, severe asthma in children

OBJECTIVE

To briefly present the current options available for the treatment of acute, severe asthma in children, with a special focus on emergency department and inpatient treatment, and to describe newer therapies that may aid treatment in the future.

DATA SOURCES AND STUDY SELECTION

A MEDLINE search (1966-May 2001) of the English-language literature pertaining to drug therapy of acute asthma was performed. Key word searches included acute asthma, albuterol, ipratropium, corticosteroids, magnesium, and theophylline. Additional articles from these sources and published national guidelines were identified. Relevant studies pertaining to current therapy of acute asthma in pediatric patients were selected; if there were minimal pediatric data, adult data were included.

DATA SYNTHESIS

Asthma is a chronic, inflammatory disorder of the airways. Acute exacerbations can occur and are challenging to manage. Albuterol, ipratropium, and systemic corticosteroids have been shown to be effective in acute asthma exacerbations. Because some patients do not respond to maximal therapy, older therapies such as magnesium and theophylline are being reevaluated. Theophylline may have some therapeutic effect, but given its toxicity profile, it is unclear whether it offers any advantage over maximal beta(2)-agonist therapy. There are only minimal published data evaluating the use of magnesium in pediatrics, and most are small trials or case reports. Newer therapies such as ventilation strategies with heliox and intravenous leukotriene modifiers currently being evaluated may or may not prove to be beneficial in the future.

CONCLUSIONS

beta(2)-agonists, ipratropium, and corticosteroids remain the most useful therapeutic agents for acute asthma exacerbations in pediatric patients. However, these agents are not ideal in all patients and, given the existing questions regarding safety and/or efficacy of available alternatives, more effective options are needed.

Acute asthma

OBJECTIVE: Asthma is the most common medical emergency in children. It is associated with significant morbidity and mortality rates and poses a tremendous societal burden worldwide. Management of the acute attack involves a stepwise approach that includes beta-agonist and steroid therapy, the mainstay of emergency treatment. Most patients will respond to this regime and can be discharged from the emergency department. Failure to respond to treatment necessitates hospital admission and sometimes admission to the intensive care unit (ICU). Management in the ICU involves intensification of pharmacologic therapy, including nonstandard therapies, in an attempt to avoid intubation and ventilation. When needed, mechanical ventilatory support can be rendered fairly safe with little morbidity if the likely cardiorespiratory physiologic derangements are appreciated and if appropriate ventilatory strategies are used. In the past two decades, the availability of newer potent medications and changes in approach to monitoring and ventilatory strategies have resulted in a decrease in ICU morbidity and mortality rates. Research endeavors are presently underway to further characterize the underlying mechanisms of the disease and are likely to lead to novel therapies. This article reviews the approach to management of acute severe asthma.

The Management of Acute Severe Asthma

Acute severe asthma exacerbations resulting in emergency department visits and hospitalization usually constitute a failure of long-term control therapy. However, even patients with relatively mild asthma can have severe life-threatening episodes. In both children and adults, viral respiratory infections are the major triggering event, although outbreaks of severe asthma have been associated with high concentrations of aeroallergens. Patients should be provided with written action plans on what to do for acute deterioration, and more severe patients may keep prednisone at home to begin after consultation with their physician. The primary therapy of acute asthma exacerbations remains frequent administration of aerosol β2-agonists and systemic corticosteroids for those patients not fully responding to the β2-agonists. Mild exacerbations may be treated with an increased dosage of inhaled corticosteroids. Patients at risk for acute exacerbations may benefit from peak flow measurement, particularly those who have difficulty perceiving airway obstruction. It is recommended that patients remain on full dose of prednisone until they achieve 70-80 percent of predicted normal or personal best peak flow. In the emergency department, the use of β2-agonists by metered-dose inhaler and holding chamber is as effective as nebulizer if given in a sufficient dose 6-10 puffs equivalent to 5 mg via nebulizer. In those patients not responding completely, the addition of ipratropium bromide has shown to produce additive bronchodilation and reduce hospitalizations. Other therapies such as magnesium sulfate, intravenous β2-agonists, heliox and ketamine have been used, but data demonstrating efficacy are insufficient to warrant recommending their general use.

Nordic consensus report on asthma management. Nordic Asthma Consensus Group

The work with the Nordic consensus report on asthma management started some years ago. The Nordic countries have common socioeconomic conditions. We acknowledge the international as well as other European guidelines providing valuable recommendations. Nevertheless, we felt the need to combine the common Nordic experiences in order to have a local statement of asthma and asthma care, based upon Nordic clinical science and tradition. The work has been rewarding and we acknowledge many valuable contributions from paediatricians, allergologists and lung physicians in all Nordic countries. The response has so far been positive and we feel that the present material reflects the main opinion of Nordic physicians taking care of asthma patients of all ages. However, the asthma and allergy research field is rapidly developing. Thus, this document should merely be regarded as a time-limited contribution to the continuing scientific discussion of this fascinating field.

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.

Comparison of two regimens of beta-adrenergics in acute asthma

BACKGROUND AND METHODS

Inhaled adrenergics and steroids are the main agents used in acute asthma. Dosing recommendations for adrenergics, while generally becoming more aggressive, lack prospective validation. A double blind, randomized trial of two regimens of nebulized metaproterenol was conducted in patients presenting to an Emergency Department with an acute asthma exacerbation. Asthmatics age 16-55, with no other cardio-pulmonary disease, presenting with peak expiratory flow rate (PEFR) < 30% of predicted and greater than 80 L/m were enrolled. All patients received 125 mg of methylprednisolone and theophylline, if needed, to reach therapeutic levels. The experimental group received 0.3 cc metaproterenol in 2.5 cc of saline at times 0, 20", 40", 1', 2', 3', 4', 5', 6', and 7'. The control group received metaproterenol at times 0, 1 hr, and hours 3, 5, and 7. Placebo was given to control group patients at 20", 40", 2', 4', and 6'. PEFR and vital signs were measured 10 min after each treatment. Study end points included discharge upon reaching set criteria or admission if patients were not discharged following the hour 7 treatment.

RESULTS

Seventy one patients were enrolled, 40 in experimental group and 31 in the control group. The group characteristics did not differ at entry in any significant way, and the groups began with mean expected PEFR of 23.4% and 24.5%, respectively. There were no significant differences at any point in PEFR outcomes, time to discharge, or admission rate. The experimental group showed a greater increase in pulse rate and a reduced diastolic blood pressure at 20, 40 and 60 min. The experimental group had a 12- and 8-fold increase in the risk of a pulse rate > 140 at 40 and 60 min, respectively. This group also had two moderate complications, both near the 60-minute mark. These were an induction of atrial fibrillation in one patient and ischemic electrocardiographic changes in another.

CONCLUSION

Three treatments in the first hour, and hourly thereafter showed no benefit over treatments initially, at one hour, and every other hour in acute, moderate, or severe exacerbation of asthma. Side effects were markedly increased in the control group. Such dosing should not be recommended as routine therapy.

Death from asthma: rare but real

Asthma mortality has been increasing over the past 15 years. Since the incidence of fatal asthma is rare, death is perceived as an unexpected outcome. This paper reviews the nature of asthma, and the circumstances and characteristics of patients with fatal asthma attacks. In light of these features, the emergency care of acute asthma is discussed. Recommendations for improvement of prehospital and hospital care are made. Despite optimum therapy and management, death is sometimes unavoidable.

Optimal pharmacologic treatment of the critically ill patient with obstructive airways disease

There are few experimental data evaluating the effect of inhaled bronchodilator treatment in the critically ill patient in the intensive care unit. Extrapolating from the data that are available in chronic and acute asthma and chronic obstructive pulmonary disease (COPD) studies, it appears that both agents may be beneficial. Beta-adrenergic receptor agonists are first-line agents in asthma. However, anticholinergics may be valuable as additive agents or as single agents if the patient is intolerant of beta-adrenergic side effects. This may be especially important in the critically ill patient with multiple organ failure in whom excessive tachycardia may reduce oxygen delivery. Anticholinergics and beta 2-adrenergic agonists both appear to be beneficial in smoking-related chronic bronchitis. Finally, because of the severity of illness in the critical care setting, both drugs should be titrated to maximal effect when possible, monitoring closely for adverse effects of the larger than normal doses that are used.

Beta-agonists in the treatment of acute exacerbation of chronic obstructive pulmonary disease

OBJECTIVE

To critically evaluate the following issues regarding the use of beta-agonists in the treatment of acute exacerbations of chronic obstructive pulmonary disease (COPD): (1) optimal dose, (2) use of nebulizer (NEB) versus metered-dose inhaler-spacer devices (MDISs), (3) comparison with anticholinergic agents, and (4) use in mechanically ventilated patients. The patient populations addressed are limited primarily to emergency department (ED) and intensive care/acute care settings.

DATA SOURCES

English-language journal articles published between 1977 and 1993.

STUDY SELECTION

Nine studies were evaluated that included beta-agonists alone or in combination with other bronchodilators in the treatment of acute exacerbation of COPD. Many of the studies contained design flaws or were limited in size, making interpretation difficult. In studies containing both asthma and COPD patients, focus was restricted to analysis of COPD patients when possible.

DATA EXTRACTION

Performed subjectively by the authors. Studies were evaluated for methodologic strengths and weaknesses.

DATA SYNTHESIS

Dosing studies in patients with stable disease show a relationship between dose and the various pulmonary function tests (PFTs). Dose also correlates with duration of action and incidence of adverse effects. Four studies compared NEBs versus MDISs. Studies revealed significant improvement in PFTs for both treatments, with no significant difference between groups noted. Five studies compared various combinations of beta-agonists and ipratropium. Both ipratropium and beta-agonists caused statistically significant increases in PFTs from baseline. Combination therapy provided no further increase in spirometry compared with that of single-agent therapy. One study did report an early discharge from the ED with the addition of ipratropium. Most studies did not use large doses of beta-agonists or evaluate the effect of repeated doses. Many studies allowed concomitant therapy. Most did not include outcome measurements, such as ED length of stay, admission rates, hospital stay, or incidence of relapse.

CONCLUSIONS

Dose-response studies in patients with stable disease suggest that doses of albuterol powder up to 1 mg may be tolerated safely, although use of repeated larger doses has not been well studied. Beta-agonists given by MDIS or NEB are equally effective in this setting. There is no apparent advantage to combined use of beta-agonist and ipratropium in the acute setting. Future research in this area should evaluate the use of larger or repeated doses of beta-agonists in the acute setting. Optimizing concurrent therapy and evaluating various patient outcomes should receive special attention in further investigations.

Emergency Department and Hospital Treatment of Asthma

Asthma is one of the most frequently treated problems in emergency departments and hospitals. Over the last 10 years, several excellent clinical trials have redefined the optimal approach to treating acute, severe asthma. Both in the emergency department and in the hospital, frequent doses of inhaled β2-agonists and systemic corticosteroids are the cornerstones of treatment. In either setting, theophylline therapy adds no or minimal benefits. Inhaled anticholinergics add to the efficacy of the initial dose only of inhaled β2-agonist in the emergency department. Pharmacists should help ensure optimal treatment in acute care settings via protocols as well as routine patient monitoring and drug use evaluation. Improving long-term prevention of asthma should also be addressed by careful patient education and treatment protocols. Serving on a case management team is one excellent approach of helping patients with asthma. Providing pharmaceutical care for asthmatics is a rewarding experience that can dramatically improve clinical outcomes, including a reduced need for emergency and hospital treatment. Copyright © 1992 by W.B. Saunders Company