Diltiazem is a calcium channel blocker that belongs to the benzothiazepine class of compounds, which features a thiazepine ring system. It is used in the treatment of angina pectoris, hypertension, and certain arrhythmias. Nifedipine and nicardipine are dihydropyridine calcium channel blockers, while verapamil is a phenylalkylamine calcium channel blocker; these belong to different structural classes.