May interfere with the prokinetic effects of cisapride and metoclopramide.
Potentially Fatal: May reduce the stimulatory effect of secretin. Concurrent use with biperiden, orphenadrine, procyclidine or trihexyphenidyl may cause anticholinergic effects such as confusion and loss of bladder control; a washout period of 1 wk between using these drugs is recommended. May increase the ulcerogenic effect of potassium chloride.
Strong CYP3A4 inhibitors (e.g. ketoconazole, fluconazole, itraconazole, erythromycin, telithromycin, clarithromycin, ritonavir, indinavir, nelfinavir, nefazodone, aprepitant, verapamil) may reduce the metabolism of solifenacin, thus increasing its plasma levels.