The concomitant use of oxybutynin with other anticholinergic drugs or with other agents which produce
dry mouth, constipation, somnolence (drowsiness), and/or other anticholinergic-like effects may increase the
frequency and/or severity of such effects.
Anticholinergic agents may potentially alter the absorption of some concomitantly administered drugs
due to anticholinergic effects on gastrointestinal motility. This may be of concern for drugs with a narrow
Mean oxybutynin chloride plasma concentrations were approximately 2 fold higher when DITROPAN XL was
administered with ketoconazole, a potent CYP3A4 inhibitor. Other inhibitors of the cytochrome P450 3A4 enzyme system,
such as antimycotic agents (e.g., itraconazole and miconazole) or macrolide antibiotics (e.g., erythromycin and
clarithromycin), may alter oxybutynin mean pharmacokinetic parameters (i.e., Cmax and AUC). The clinical
relevance of such potential interactions is not known. Caution should be used when such drugs are
Concurrent ingestion of antacid (20 mL of antacid containing aluminum hydroxide, magnesium hydroxide,
and simethicone) did not significantly affect the exposure of oxybutynin or desethyloxybutynin.