Plasma concentrations and effects of salbutamol administered orally to patients with cystic fibrosis.

1. To test whether cystic fibrosis (CF) altered the kinetics and dynamics of oral salbutamol, 11 patients with CF (19-33 years old; five females; FEV1: 37 +/- 12% of predicted value) and 10 healthy volunteers (20-41 years old; five females; FEV1: 99 +/- 14% of predicted value) received orally 4 mg salbutamol. 2. The estimated pharmacokinetic parameters of salbutamol in patients with CF were identical to those in healthy subjects. For instance, peak plasma concentrations of salbutamol were 10.5 +/- 2.6 (mean +/- s.d.) and 10.2 +/- 2.9 ng ml-1 (NS), and the area under salbutamol plasma concentrations as a function of time (AUC (0, 7 h)) was 43.0 +/- 9.3 ng ml-1 h and 43.3 +/- 12.7 ng ml-1 h (NS) in CF patients and in healthy subjects, respectively. Since on a mg kg-1 dose basis, CF patients received a dose 28% greater than healthy subjects, this lack of differences implies a decrease in the amount of salbutamol absorbed, or alternatively, an increase in both clearance and volume of distribution of salbutamol. 3. Salbutamol did not elicit bronchodilation in CF patients, but increased heart rate from 77 +/- 2 to 103 +/- 3 beats min-1 (P < 0.05). 4. Salbutamol decreased plasma potassium concentrations from 4.5 +/- 0.1 to 3.8 +/- 0.1 mmol l-1 in the CF group (P < 0.05) and from 4.1 +/- 0.2 to 3.4 +/- 0.1 mmol l-1 in the controls (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)