Erythromycin, fluoxetine, protease-inhibitors and azole-derivatives No clinical interaction studies have been performed between nifedipine and active substances that inhibit the CYP3A4 system, like erythromycin, fluoxetine, protease-inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, saquinavir) and azole-derivatives (ketoconazole, itraconazole and fluconazole).