Levalbuterol nebulizer solution: is it worth five times the cost of albuterol?

Indian Guidelines on Nebulization Therapy

Inhalational therapy, today, happens to be the mainstay of treatment in obstructive airway diseases (OADs), such as asthma, chronic obstructive pulmonary disease (COPD), and is also in the present, used in a variety of other pulmonary and even non-pulmonary disorders. Hand-held inhalation devices may often be difficult to use, particularly for children, elderly, debilitated or distressed patients. Nebulization therapy emerges as a good option in these cases besides being useful in the home care, emergency room and critical care settings. With so many advancements taking place in nebulizer technology; availability of a plethora of drug formulations for its use, and the widening scope of this therapy; medical practitioners, respiratory therapists, and other health care personnel face the challenge of choosing appropriate inhalation devices and drug formulations, besides their rational application and use in different clinical situations. Adequate maintenance of nebulizer equipment including their disinfection and storage are the other relevant issues requiring guidance. Injudicious and improper use of nebulizers and their poor maintenance can sometimes lead to serious health hazards, nosocomial infections, transmission of infection, and other adverse outcomes. Thus, it is imperative to have a proper national guideline on nebulization practices to bridge the knowledge gaps amongst various health care personnel involved in this practice. It will also serve as an educational and scientific resource for healthcare professionals, as well as promote future research by identifying neglected and ignored areas in this field. Such comprehensive guidelines on this subject have not been available in the country and the only available proper international guidelines were released in 1997 which have not been updated for a noticeably long period of over two decades, though many changes and advancements have taken place in this technology in the recent past. Much of nebulization practices in the present may not be evidence-based and even some of these, the way they are currently used, may be ineffective or even harmful. Recognizing the knowledge deficit and paucity of guidelines on the usage of nebulizers in various settings such as inpatient, out-patient, emergency room, critical care, and domiciliary use in India in a wide variety of indications to standardize nebulization practices and to address many other related issues; National College of Chest Physicians (India), commissioned a National task force consisting of eminent experts in the field of Pulmonary Medicine from different backgrounds and different parts of the country to review the available evidence from the medical literature on the scientific principles and clinical practices of nebulization therapy and to formulate evidence-based guidelines on it. The guideline is based on all possible literature that could be explored with the best available evidence and incorporating expert opinions. To support the guideline with high-quality evidence, a systematic search of the electronic databases was performed to identify the relevant studies, position papers, consensus reports, and recommendations published. Rating of the level of the quality of evidence and the strength of recommendation was done using the GRADE system. Six topics were identified, each given to one group of experts comprising of advisors, chairpersons, convenor and members, and such six groups (A-F) were formed and the consensus recommendations of each group was included as a section in the guidelines (Sections I to VI). The topics included were: A. Introduction, basic principles and technical aspects of nebulization, types of equipment, their choice, use, and maintenance B. Nebulization therapy in obstructive airway diseases C. Nebulization therapy in the intensive care unit D. Use of various drugs (other than bronchodilators and inhaled corticosteroids) by nebulized route and miscellaneous uses of nebulization therapy E. Domiciliary/Home/Maintenance nebulization therapy; public & health care workers education, and F. Nebulization therapy in COVID-19 pandemic and in patients of other contagious viral respiratory infections (included later considering the crisis created due to COVID-19 pandemic). Various issues in different sections have been discussed in the form of questions, followed by point-wise evidence statements based on the existing knowledge, and recommendations have been formulated.

Transforming Separation Science with Single-Molecule Methods

Empirical optimization of the multiscale parameters underlying chromatographic and membrane separations leads to enormous resource waste and production costs. A bottom-up approach to understand the physical phenomena underlying challenges in separations is possible with single-molecule observations of solute-stationary phase interactions. We outline single-molecule fluorescence techniques that can identify key interactions under ambient conditions. Next, we describe how studying increasingly complex samples heightens the relevance of single-molecule results to industrial applications. Finally, we illustrate how separation methods that have not been studied at the single-molecule scale can be advanced, using chiral chromatography as an example case. We hope new research directions based on a molecular approach to separations will emerge based on the ideas, technologies, and open scientific questions presented in this Perspective.

Complications and Pharmacologic Interventions of Invasive Positive Pressure Ventilation During Critical Illness

Objective: To review the fundamentals of invasive positive pressure ventilation (IPPV) and the common complications and associated pharmacotherapeutic management in order to provide opportunities for pharmacists to improve patient outcomes. Data Sources: A MEDLINE literature search (1950-December 2017) was performed using the key search terms invasive positive pressure ventilation, mechanical ventilation, pharmacist, respiratory failure, ventilator associated organ dysfunction, ventilator associated pneumonia, ventilator bundles, and ventilator liberation. Additional references were identified from a review of literature citations. Study Selection and Data Extraction: All English-language original research and review reports were evaluated. Data Synthesis: IPPV is a common supportive care measure for critically ill patients. While lifesaving, IPPV is associated with significant complications including ventilator-associated pneumonia, sinusitis, organ dysfunction, and hemodynamic alterations. Optimization of pain and sedation management provides an opportunity for pharmacists to directly affect IPPV exposure. A number of pharmacotherapeutic interventions are related directly to prophylaxis against IPPV-associated adverse events or aimed at reduction of duration of IPPV. Conclusions: Enhanced knowledge of the common complications, associated pharmacotherapy, and monitoring strategies facilitate the pharmacist's ability to provide increased pharmacotherapeutic insight in a multidisciplinary intensive care unit setting.

Source discrimination of drug residues in wastewater: The case of salbutamol

Analytical methods used for pharmaceuticals and drugs of abuse in sewage play a fundamental role in wastewater-based epidemiology (WBE) studies. Here quantitative analysis of drug metabolites in raw wastewaters is used to determine consumption from general population. Its great advantage in public health studies is that it gives objective, real-time data about community use of chemicals, highlighting the relationship between environmental and human health. Within a WBE study on salbutamol use in a large population, we developed a procedure to distinguish human metabolic excretion from external source of contamination, possibly industrial, in wastewaters. Salbutamol is mainly excreted as the sulphate metabolite, which is rapidly hydrolyzed to the parent compound in the environment, so this is currently not detected. When a molecule is either excreted un-metabolized or its metabolites are unstable in the environment, studies can be completed by monitoring the parent compound. In this case it is mandatory to assess whether the drug in wastewater is present because of population use or because of a specific source of contamination, such as industrial manufacturing waste. Because commercial salbutamol mainly occurs as a racemic mixture and is stereoselective in the human metabolism, the enantiomeric relative fraction (EFrel) in wastewater samples should reflect excretion, being unbalanced towards one of two enantiomers, if the drug is of metabolic origin. The procedure described involves chiral analysis of the salbutamol enantiomers by liquid chromatography-tandem mass spectrometry (LC-MS-MS) and calculation of EFrel, to detect samples where external contamination occurs. Samples were collected daily between October and December 2013 from the Milano Nosedo wastewater treatment plant. Carbamazepine and atenolol were measured in the sewage collector, as "control" drugs. Salbutamol EFrel was highly consistent in all samples during this three-month period, but a limited number of samples had unexpectedly high concentrations where the EFrel was close to that observed of the un-metabolized, commercially available drug, supporting the idea of an external source of contamination, besides human metabolic excretion. Results showed that, when present, non-metabolic daily loads could be evaluated indicating an average of 4.12g/day of salbutamol extra load due to non-metabolic sources. The stereoselectivity in metabolism and enantiomeric ratio analysis appears to be a useful approach in WBE studies to identify different sources of drugs in the environment, when no metabolic products are present at useful analytical levels.

An aerosol formulation of R-salbutamol sulfate for pulmonary inhalation

An aerosol formulation containing 7.5 mg of R-salbutamol sulfate was developed. The aerosol was nebulized with an air-jet nebulizer, and further assessed according to the new European Medicines Agency (EMA) guidelines. A breath simulator was used for studies of delivery rate and total amount of the active ingredient at volume of 3 mL. A next generation impactor (NGI) with a cooler was used for analysis of the particle size and in vitro lung deposition rate of the active ingredient at 5 °C. The anti-asthmatic efficacy of the aerosol formulation was assessed in guinea pigs with asthma evoked by intravenous injection of histamine compared with racemic salbutamol. Our results show that this aerosol formulation of R-salbutamol sulfate met all the requirements of the new EMA guidelines for nebulizer. The efficacy of a half-dose of R-salbutamol equaled that of a normal dose of racemic salbutamol.

Childhood asthma: a guide for pediatric emergency medicine providers

Pediatric asthma is a disease that is managed across outpatient physicians, hospitalists, critical care physicians, and emergency department (ED) physicians. Scoring systems may facilitate a rapid assessment of the child with asthma in the ED. Short-acting beta agonists are still the mainstay of therapy for acute exacerbations along with corticosteroids and ipratropium bromide. ED providers must also know the indications for noninvasive ventilation and intubation. Most patients can be treated and discharged from the ED after acute exacerbation, and should be given a plan for going home that provides educational material and emergency scenarios to help prevent future acute incidents.

Effect of bronchodilator treatment on the incidence of postoperative atrial fibrillation after cardiac surgery

OBJECTIVE

We sought to examine the effects of bronchodilator treatment on the incidence of postoperative atrial fibrillation (POAF) after cardiac surgery.

METHODS

A cross-sectional design using a retrospective chart review was performed in patients who underwent cardiac surgery. Those who had previous atrial fibrillation or preoperative bronchodilator treatment were excluded from the final sample (n = 506). The Statistical Package for the Social Sciences (SPSS, Inc., Chicago, IL) was used for statistical analyses.

RESULTS

The incidence of POAF in this study was 27.9%, and was associated with age (P < .01) and type of cardiac surgery (P < .05), indicating that increasing age, and combined cardiac surgery were more likely to precipitate POAF. Bronchodilator treatment did not increase POAF. However, combined therapy significantly (P < .01) precipitated more POAF (48.7%) than did albuterol (21.4%) or levalbuterol (18.5%).

CONCLUSIONS

Postoperative atrial fibrillation continues to be a common complication after cardiac surgery. Bronchodilator treatment with either albuterol or levalbuterol did not precipitate POAF, unless both agents were given to the same patients postoperatively.

Common pediatric respiratory emergencies

Pediatric respiratory illnesses are a huge burden to emergency departments worldwide. This article reviews the latest evidence in the epidemiology, assessment, management, and disposition of children presenting to the emergency department with asthma, croup, bronchiolitis, and pneumonia.

Albuterol and levalbuterol use and spending in Medicare beneficiaries with chronic obstructive pulmonary disease

BACKGROUND

The evidence for the benefits of branded levalbuterol over generic albuterol in patients with chronic obstructive pulmonary disease (COPD) is inconclusive. However, there are significant cost differences between these products.

OBJECTIVES

This study examined use and spending on albuterol and levalbuterol in a nationally representative sample of Medicare beneficiaries with COPD enrolled in Part D in 2006. It also examined differences in patient characteristics and use of other COPD drugs among recipients of these 2 short-acting β-agonists.

METHODS

Data were obtained from the 5% Medicare files for 2005-2006 linked to the 2006 Medicare Part D files. The sample consisted of all fee-for-service beneficiaries with COPD enrolled in stand-alone Part D plans in 2006. Patient characteristics and other COPD medication use were compared across albuterol-only users, levalbuterol-only users, and users of both albuterol and levalbuterol. Multinomial logistic regressions were used to identify factors independently associated with levalbuterol use.

RESULTS

There were 5.5 times more albuterol users than levalbuterol users in 2006; however, mean annual spending on levalbuterol was 18.6 times higher per user in 2006 than spending on albuterol ($1876 vs $101 per user, respectively). Levalbuterol-only users were more likely to be older than albuterol-only users (mean age: 71.5 vs 68.7 years; P < 0.05), as well as sicker (mean prescription drug hierarchical condition category score: 1.72 vs 1.55; P < 0.05) and residing in the South (67.9% vs 41.6%; P < 0.05). Levalbuterol-only users were more likely to use nebulizer forms covered under Part B than inhaler forms covered under Part D (78.6% vs 26.8%, respectively; P < 0.05), whereas albuterol-only users were more likely to use inhaler forms covered under Part D than nebulizer forms covered under Part B (82.2% vs 33.0%, respectively; P < 0.05).

CONCLUSIONS

In this sample of Medicare beneficiaries with COPD enrolled in Part D, mean annual spending in 2006 was significantly higher for levalbuterol than for albuterol. The differences between levalbuterol and albuterol users in terms of patient characteristics, geographic region, and drug formulation/device type, coupled with the inconclusive evidence for efficacy differences in the literature, highlight the need for further comparative clinical and cost-effectiveness studies of these agents.

(R)-albuterol for asthma: pro [a.k.a. (S)-albuterol for asthma: con]

Is there scientific evidence to support the replacement of the beta-agonist racemic albuterol with levalbuterol--that is, (R)-albuterol? The argument presented further refines the question as "Do we wish to continue to treat asthma with a mixture of albuterol, of which half is an agent with no known benefit--that is, (S)-albuterol--and which may exacerbate the disease?"

Asthma pathophysiology and evidence-based treatment of severe exacerbations

PURPOSE

The pathogenesis of asthma and the treatment approach for acute exacerbations are described. The pharmacology, efficacy, safety, and cost of the beta2 agonist, albuterol, a racemic mixture of equal amounts of R- and S-enantiomers, and levalbuterol, the R-enantiomer, are compared.

SUMMARY

Asthma symptoms are the result of bronchial hyperresponsiveness, bronchospasm, and chronic airway inflammation. Short-acting, inhaled beta2 agonists; oxygen; intravenous fluids; and corticosteroids are the mainstays of treatment for acute exacerbations. The R-enantiomer of albuterol is responsible for bronchodilation. The S-enantiomer exhibits broncho-constricting activity in vitro, which may be mediated by muscarinic receptors and may be opposed by adding the anticholinergic agent ipratropium bromide. Levalbuterol improves pulmonary function to a greater extent than racemic albuterol and reduces the need for costly hospitalizations in patients with acute asthma exacerbations.

CONCLUSION

Levalbuterol is an alternative to racemic albuterol with the potential to improve patient outcomes and reduce costs in the treatment of acute asthma exacerbations.

Clinical efficacy of racemic albuterol versus levalbuterol for the treatment of acute pediatric asthma

STUDY OBJECTIVE

An efficacy treatment study is conducted comparing levalbuterol to racemic albuterol for acute pediatric asthma in the emergency department (ED).

METHODS

This was a prospective, double-blind, randomized, controlled study involving 129 children (2 to 14 years), presenting to a pediatric ED with an acute moderate or severe asthma exacerbation. Children were treated using a standard ED asthma pathway. Primary outcomes were changes from baseline in clinical asthma score and the percentage of predicted forced expiratory volume in 1 second after the first, third, and fifth treatment. Secondary outcomes included number of treatments, length of ED care, rate of hospitalization, and changes in pulse rate, respiratory rate, and oxygen saturation. Occurrence of adverse events was recorded.

RESULTS

Sixty-four children in the racemic albuterol and 65 children in the levalbuterol group completed the study. There were no differences between groups in primary outcomes, secondary outcomes, or adverse events.

CONCLUSION

There was no difference in clinical improvement in children with acute moderate to severe asthma exacerbations treated with either racemic albuterol or levalbuterol.

Comparison of racemic albuterol and levalbuterol in the treatment of acute asthma in the ED

BACKGROUND

Acute asthma is often treated with racemic albuterol, a 1:1 mixture of (R)-albuterol and (S)-albuterol. Levalbuterol is the single-isomer agent comprised (R)-albuterol, an active bronchodilator, without any effects of (S)-albuterol.

OBJECTIVE

To compare emergency department (ED) admission rates of patients presenting with acute asthma who were treated with either racemic albuterol or levalbuterol.

SETTING

Suburban community teaching hospital.

DESIGN

Retrospective observational case review.

METHODS

Emergency department patients presenting with acute asthma at 2 different sites were reviewed over 9- and 3-month consecutive periods. Outcome measures included ED hospital admission rate, length of stay, arrival acuity, and treatment costs. Patients were excluded if younger than 1 year or if no treatment of acute asthma was rendered.

RESULTS

Of the initial 736 consecutive cases, significantly fewer admissions (4.7% vs 15.1%, respectively; P = .0016) were observed in the levalbuterol vs racemic albuterol group. Of the subsequent 186 consecutive cases, significantly fewer admissions were also observed (13.8% vs 28.9%, respectively; P = .021) in the levalbuterol vs racemic albuterol group. Treatment costs were lower with levalbuterol mainly because of a decrease in hospital admissions.

CONCLUSION

Levalbuterol treatment in the ED for patients with acute asthma resulted in higher patient discharge rates and may be a cost-effective alternative to racemic albuterol.

Comparison of levalbuterol and racemic albuterol combined with ipratropium bromide in acute pediatric asthma: a randomized controlled trial

Our study compared levalbuterol (LEV) to the combination of racemic albuterol (RAC) and ipratropium bromide (IB) in 140 patients aged 6-18 years presenting to a tertiary hospital Emergency Department with acute asthma and a peak expired flow rate (PEF)<80% predicted. Patients were randomized to: LEV (<or=6 nebs LEV 1.25 mg); or RAC/IB (<or=3 nebs RAC 5.0 mg+IB 0.25 mg followed as needed by <or=3 nebs RAC 5.0 mg). No difference was noted in the study population (mean age 11.6 years and initial mean predicted PEF 49.5%) between LEV (n=72) and RAC/IB (n=68) for study outcomes except for measures of heart rate (HR). Median % HR increase for RAC/IB (26%) exceeded LEV (9%) (p<0.001). In a sample of children with acute asthma and initial mean PEF<50% predicted, LEV was associated with less tachycardia but had no other advantage over RAC combined with IB.

Automatic replacement of albuterol nebulizer therapy by metered-dose inhaler and valved holding chamber

PURPOSE

Evidence supporting the delivery of bronchodilators with a metered-dose inhaler and a valved holding chamber (MDI+VHC) in place of a small-volume nebulizer (SVN) is discussed, and the steps taken to accomplish such a conversion program at one institution are described.

SUMMARY

Double-blind, randomized studies in patients with acute exacerbations of asthma have demonstrated that higher doses of albuterol delivered by MDI+VHC (4-10 puffs per dose) are as effective as 2.5 mg of albuterol sulfate delivered by SVN. Three double-blind studies support the conclusion that the two methods are equivalent with respect to both efficacy and adverse effects in patients with chronic obstructive pulmonary disease. MDI+VHC offers practical advantages over SVN, including the capacity for home use by the patient, portability, less setup time, and no need for daily disinfection. Pharmacists and respiratory therapists obtained approval through the pharmacy and therapeutics committee for respiratory therapists to convert orders for bronchodilators delivered by SVN to administration by MDI+VHC. The conversion policy allows physicians to override it, but none have exercised this option. On intensive care units (ICUs), the policy resulted in a 53% increase in the use of MDI+VHC during the six-month period after it went into effect. Respiratory therapists have been less thorough in implementing the policy for non-ICU patients.

CONCLUSION

Delivery of bronchodilators by MDI+VHC is as effective as delivery by SVN but offers several advantages. A policy to switch patients from SVN to MDI+VHC for bronchodilator administration met with limited success.

Retrospective comparison of nebulized levalbuterol and albuterol for adverse events in patients with acute airflow obstruction

The objective of this study was to retrospectively compare the mean change in heart rate (HR) of patients with acute airflow obstruction treated with nebulized levalbuterol vs. albuterol. The study was conducted at the Akron General Medical Center, a 537-bed adult tertiary care teaching and research medical center. The participants were patients (> or = 18 years old) presenting to the emergency department with acute airflow obstruction. This was a retrospective chart review. Treatment groups received either levalbuterol (0.63 mg) or albuterol (2.5 mg). Respiratory care notes record HRs before and after nebulization of levalbuterol or albuterol. Primary analysis was conducted on days 1 and 3 of therapy to determine whether there is a difference between levalbuterol and albuterol with regard to mean change in HR with each treatment. In the primary analysis data, 35 subjects in each treatment group were compared. The mean age (+/- SD) was 65 +/- 16.4 and 68 +/- 16.5 for levalbuterol and albuterol, respectively. On day 1 of therapy, the difference in the mean change in HR with albuterol compared with levalbuterol was 1.0 bpm (95% CI, -1.6 to 3.7). On day 3, a statistically significant difference occurred in mean change in HR between treatment groups at 2.7 bpm (95% CI, 0.02 to 5.4). An increase in HR of 2.7 bpm by albuterol compared with levalbuterol on day 3 of therapy was the only significant finding among the analyses. However, this finding did not demonstrate dangerous elevations in HR following treatment with albuterol. Even the upper end of the confidence interval range at 5.4 bpm does not support a clinically significant difference in tachycardia with the pure isomer compared with the racemic mixture during acute airway obstruction.

Single-isomer levalbuterol: a review of the acute data

Levalbuterol, the pure (R)-isomer of racemic albuterol, is a new therapeutic option for patients with asthma. Racemic albuterol comprises a 50:50 mixture of (R)- and (S)-albuterol, with (R)-albuterol conferring all of the bronchodilator effects of the racemate. Numerous preclinical and in vitro studies have indicated that (S)-albuterol is not an inert isomer, but may have proinflammatory effects. Results from clinical trials in adults and children with asthma have demonstrated that 0.63 mg levalbuterol provides effective bronchodilation with lower b-mediated side effects compared with 2.5 mg racemic albuterol. In the emergency department, levalbuterol provided greater bronchodilation and significantly reduced hospital admissions compared with racemic albuterol. Recent studies have supported that levalbuterol use in acute settings may reduce the cost of asthma treatment by decreasing the total treatments and subsequent respiratory therapy resources. Levalbuterol provides heath care professionals with a safe, effective, and potentially cost-saving alternative to racemic albuterol for the treatment of patients with asthma.

Management of acute exacerbations of chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease are at high risk for acute exacerbations. Strategies that may prevent exacerbations are smoking cessation, pulmonary rehabilitation, and influenza vaccination. Therapy includes bronchodilators, corticosteroids, and antibiotics. Rapid-acting beta2-agonists are bronchodilating agents of choice. Ipratropium should be considered in patients who fail or cannot tolerate beta2-agonists. Data do not support combining anticholinergics and beta2-agonists in acute exacerbations; however, new data do support systemic corticosteroids for their role in reducing airway inflammation. Antibiotics should be included in the regimen if two of the three following are present: increased dyspnea, increased sputum volume, and increased sputum purulence. Many exacerbations may be caused by viruses or noninfective sources, in which case antibiotics are not indicated. Oxygen administration with or without assisted ventilation may be required for short-term management.

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.

Single-isomer beta-agonists

A new generation of bronchodilators is being developed for acute asthma management-single-isomer beta-agonists. These drugs consist only of the active bronchodilatory isomer (eutomer); they do not have the inactive and potentially harmful isomer (distomer) that is present in marketed racemic beta-agonists. Clinical studies comparing the effectiveness of (R)-albuterol (levalbuterol) with racemic albuterol established a strong rationale for using single-isomer beta-agonists in place of the racemic mixture: reduced dosages provide equivalent bronchodilatory effects with fewer beta-mediated side effects. Higher dosages achieve superior bronchodilation in episodes of severe asthma and may reduce costs of emergency department treatment.

The pharmacokinetics of levosalbutamol: what are the clinical implications?

Salbutamol (albuterol) is a beta2-adrenoceptor agonist used as a bronchodilator for the treatment of asthma and as a uterine relaxant for the suspension of premature labour. Salbutamol has been marketed as a racemic mixture, although beta2-agonist activity resides almost exclusively in the (R)-enantiomer. The enantioselective disposition of salbutamol and the possibility that (S)-salbutamol has adverse effects have led to the development of an enantiomerically pure (R)-salbutamol formulation known as levosalbutamol (levalbuterol). Salbutamol is metabolised almost exclusively by sulphotransferase (SULT) 1A3 to an inactive metabolite. (R)-Salbutamol is metabolised up to 12 times faster than (S)-salbutamol. This leads to relatively higher plasma concentrations of (S)- salbutamol following all routes of administration, but particularly following oral administration because of extensive metabolism by the intestine. Enantiomer concentrations are similar for the first hour following an inhaled dose, reflecting the fact that salbutamol in the lung probably undergoes little metabolism. Subsequently, (S)-salbutamol predominates due to absorption and metabolism of the swallowed portion of the inhaled dose. Following oral or inhaled administration of enantiomerically pure salbutamol, a small amount (6%) is converted to the other enantiomer, probably by acid-catalysed racemisation in the stomach. Tissue binding of salbutamol is not enantioselective and plasma protein binding is relatively low. Both enantiomers are actively excreted into the urine. Compared with healthy individuals, patients with asthma do not have substantially different pharmacokinetics of the salbutamol enantiomers, but they do appear to have less drug delivered to the lung following inhaled administration because of their narrowed airways. Levosalbutamol elicits an equal or slightly larger response than an equivalent dose of the racemic mixture. This is probably due to competitive inhibition between the enantiomers at beta-adrenoceptors. Pharmacokinetic-pharmacodynamic relationships for levosalbutamol show relatively large interindividual variations. Functionally significant genetic polymorphisms have been identified for beta2-adrenoceptors, SULT1A3 and organic action transporters, all of which affect the disposition or action of levosalbutamol. Animal, in vitro and some clinical studies have reported deleterious effects of (S)-salbutamol on smooth muscle contractility or lung function. However, well-designed clinical studies in patients with asthma have failed to find evidence of significant toxicity associated with (S)-salbutamol. The clinical consequences of relatively higher plasma concentrations of (S)-salbutamol following administration of racemate remain unclear, but in the absence of clear evidence of toxicity the clinical superiority of levosalbutamol over racemic salbutamol appears to be small.