[Effects of adrenergic beta 2 agonists by oral route on theophylline blood levels].

Several drugs interfere with theophylline pharmacokinetics, inducing changes on it's serum levels. With the purpose of determining a possible influence of oral administered beta-2-adrenergics agents on theophylline serum levels ten patients with bronchial obstruction, whose ages ranged from 51 to 69 (average 59.90 +/- 6.67) years, were analysed. After a period of 24 hours without any medication, the patients received 600 mg of oral slow release theophylline per day, for 7 days, followed by 7 days of the same dose of theophylline combined with 16 mg of oral salbutamol. Blood samples were drawn after the 24 hours without medication and at the 4th hour after the morning dose of theophylline, at the end of each week. The serum levels were, respectively, 2.08 +/- 1.20 micrograms/ml, 15.18 +/- 6.87 micrograms/ml and 11.45 +/- 5.15 micrograms/ml. The levels of the phase (theophylline alone) were significantly higher than those obtained after the concurrent use of theophylline and salbutamol. It can be concluded that this association interferes on theophylline pharmacokinetics. We suggest that in patients taking these drugs the serum levels of theophylline shall be measured to permit an eventual correction of the dose of theophylline being administered.