 The substance is metabolized by the liver enzyme CYP3A4.Consequently, CYP3A4 inducers such as rifampicin or carbamazepine could reduce the effectiveness of nisoldipine, while CYP3A4 inhibitors such as ketoconazole increase the amount of nisoldipine in the body more than 20-fold.Grapefruit juice also increases nisoldipine concentrations by inhibiting CYP3A4.