Both
verapamil and
diltiazem are principally metabolised by CYP3A4, and also inhibit this isoenzyme. They are therefore affected by drugs that induce or inhibit CYP3A4, and also themselves affect drugs metabolised by CYP3A4. Many of the dihydropyr- idine-type calcium-channel blockers are also metabolised by CYP3A4, and are affected by inducers or inhibitors of this isoenzyme. However, they do not generally inhibit CYP3A4 or other isoenzymes to a clinically relevant extent. The exception is perhaps nicardipine, which may cause a clinically relevant inhibition of CYP3A4.