Increased theophylline clearance in asthmatic patients due to terbutaline.
The pharmacokinetic mechanism of the theophylline-terbutaline interaction has been studied. Sustained release theophylline 200-400 mg b.d. was given with placebo or terbutaline 2.5 mg t.d.s. to six adult asthmatic patients. Terbutaline decreased the serum trough theophylline levels from 8.1 to 7.3 micrograms/ml, improved daily the clinical score from 1.51 to 1.26 and increased the peak expiratory flow rate from 316 to 370 l/min. In a single dose study following the chronic therapy, it was shown that there was no change in the peak theophylline concentration or in the timing of the peak, but the t1/2 was reduced from 9.0 to 7.5 h, and the systemic clearance was increased from 20.2 to 24.8 ml.h-1.kg-1. Thus, terbutaline reduced the serum theophylline concentration by increasing its systemic clearance.
Garty
M
M
Clinical Pharmacology Unit, Beilinson Medical Center, Tel Aviv University Sackler, Medical School, Israel.
Paul-Keslin
L
L
Ilfeld
D N
DN
Mazar
A
A
Spitzer
S
S
Rosenfeld
J B
JB
D000328:Adult; D001249:Asthma / Q000188:drug therapy / Q000378:metabolism*; D003692:Delayed-Action Preparations; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013726:Terbutaline / Q000008:administration & dosage / Q000494:pharmacology*; D013806:Theophylline / Q000493:pharmacokinetics*
D003692:Delayed-Action Preparations; D013806:Theophylline; D013726:Terbutaline