<p>Darifenacin has known drug-drug interaction with CYP3A4 inhibitors (e.g. ketoconazole, itraconazole, ritonavir, nelfinavir etc.). The concomitant use of Darifenacin with other anticholinergic agents may increase the frequency and/or severity of dry mouth, constipation, blurred vision and other anticholinergic pharmacological effects.</p>