Specificity of the inhibitory effect of dextropropoxyphene on oxidative drug metabolism in man: effects on theophylline and tolbutamide disposition.

Two groups of six healthy male volunteers were studied to assess the possibility of an interaction between dextropropoxyphene and theophylline or tolbutamide using a randomised, crossover design. Subjects received theophylline 125 mg 8 hourly or tolbutamide 500 mg i.v. with and without dextropropoxyphene hydrochloride 65 mg 8 hourly. Theophylline 8‐hydroxylation was reduced by a mean of 17% but there were no changes in theophylline 1‐demethylation, theophylline 3‐ demethylation or tolbutamide hydroxylation. 1987 The British Pharmacological Society