Effects of roxatidine acetate hydrochloride and cimetidine on the pharmacokinetics of theophylline in healthy subjects.

The effects of roxatidine acetate hydrochloride and cimetidine during multiple dosing on the pharmacokinetics of theophylline was studied in nine healthy volunteers, five smokers and four non-smokers, in comparison with placebo treatment. Cimetidine reduced the terminal elimination rate constant and the total body clearance of theophylline from 0.119 to 0.101 h-1 (p less than 0.05) and from 31.2 to 26.5 ml/min (p less than 0.05), respectively, in comparison with those of placebo. There was no significant change in the volume of distribution (16.3 l for placebo and 15.5 l for cimetidine) and the renal clearance (4.5 ml/min for placebo and 3.9 ml/min for cimetidine). Roxatidine acetate hydrochloride did not significantly influence theophylline disposition in comparison with placebo treatment. The interaction of cimetidine on theophylline disposition was observed in both smokers and non-smokers, but the degree was greater in smokers.