Effects of Therapeutic Doses of Albuterol on β₂-Adrenergic Receptor Density and Metabolic Changes

Abstract

β₂-Agonist drugs at inhaled supratherapeutic doses or when given orally or parenterally alter peripheral lymphocyte β₂-adrenoceptor density (βAR) and have demonstrable metabolic effects. However, it is not known whether these changes occur at therapeutic inhaled doses. We therefore studied the effects of therapeutic doses of inhaled albuterol in five asthmatic subjects (mean age 23.0 ±2.4 years) and six normal subjects (mean age 28.3 ± 3.3 years). Subjects were studied in a randomized, double-blind protocol in which each subject received either inhaled albuterol (270 μg four times daily) for 2 weeks followed by placebo or vice versa in two sequential 2-week periods separated by a 2-week washout period. In the asthmatics, baseline FEV₁ increased significantly (p < 0.05) after 2 weeks of inhaled albuterol treatment compared to the initial visit and after 2 weeks of placebo (mean FEV₁: 3.2 L ± 0.7 L, 2.9 L ± 0.5 L, and 3.0 L ± 0.7 L, respectively). Baseline peripheral lymphocyte βAR was not significantly different (p > 0.05) between the asthmatic (mean: 757 ± 176) and normal subjects (mean: 732 ± 251). However, in neither group was there any significant change (p > 0.05) in βAR or plasma potassium, insulin, or glucose, either acutely or after 2 weeks of albuterol therapy. The present study confirms that there is no difference in peripheral lymphocyte βAR between asthmatic and normal subjects and also shows that at therapeutic doses of inhaled albuterol, there are no significant changes in βAR or metabolic effects.

• β₂-Agonists
• β₂-Adrenoceptors
• Asthma
• Plasma potassium