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

J Allergy Clin Immunol. 2001 Nov;108(5):726-31. doi: 10.1067/mai.2001.119152.


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.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Albuterol / adverse effects
  • Albuterol / chemistry*
  • Albuterol / pharmacokinetics
  • Albuterol / therapeutic use*
  • Asthma / drug therapy*
  • Asthma / metabolism
  • Bronchodilator Agents / adverse effects
  • Bronchodilator Agents / chemistry*
  • Bronchodilator Agents / pharmacokinetics
  • Bronchodilator Agents / therapeutic use*
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Female
  • Forced Expiratory Volume / drug effects
  • Heart Rate / drug effects
  • Humans
  • Male
  • Middle Aged
  • Potassium / blood
  • Stereoisomerism


  • Bronchodilator Agents
  • Albuterol
  • Potassium