Inhibition of theophylline elimination by diltiazem therapy.
To investigate the effects of diltiazem on theophylline pharmacokinetics, nine healthy male subjects (four smokers and five nonsmokers) received intravenous aminophylline (6 mg/kg) prior to and following 10 days of oral diltiazem therapy. Theophylline half-life increased significantly whereas total body clearance showed a significant decrease following diltiazem. Volume of distribution was unchanged. The small group of smokers had a significantly greater increase in theophylline half-life than the nonsmokers. Inhibition of metabolism of theophylline by diltiazem likely explains the significant changes in theophylline pharmacokinetics. A clinically important drug interaction may occur with theophylline when diltiazem therapy is given concurrently.
Department of Medicine, Mary Imogene Bassett Hospital, Cooperstown, New York 13326.
A N
AN
Nafziger
J J
JJ
May
J S
JS
Bertino
D000328:Adult; D000628:Aminophylline / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D004110:Diltiazem / Q000493:pharmacokinetics*; D004347:Drug Interactions; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D012907:Smoking / Q000097:blood; D013806:Theophylline / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D000628:Aminophylline; D013806:Theophylline; D004110:Diltiazem