title: Selective inhibitory effects of nifedipine and verapamil on oxidative metabolism: effects on theophylline.
abstract: Nine healthy male volunteers were studied to assess the possibility of an interaction between theophylline and nifedipine or verapamil using a randomised, crossover design. Subjects received theophylline 125 mg 8 hourly with and without nifedipine 20 mg 12 hourly and verapamil 80 mg 8 hourly. Nifedipine treatment reduced mean total theophylline clearance by 9%, due to decreased clearances via 1- and 3-demethylation. Verapamil treatment reduced mean total theophylline clearance by 14%, due to decreased clearances via 1- and 3-demethylation and 8-hydroxylation. Verapamil and nifedipine at usual clinical doses are unlikely to cause clinically significant changes in theophylline disposition.
authors: Department of Clinical Pharmacology, Flinders Medical Centre, Bedford Park, South Australia.
authors: R A
authors: RA
authors: Robson
authors: J O
authors: JO
authors: Miners
authors: D J
authors: DJ
authors: Birkett
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D010084:Oxidation-Reduction; D013806:Theophylline / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D013806:Theophylline; D014700:Verapamil; D009543:Nifedipine