Which of the following is a calcium channel blocker?

• A. Amlodipine
• B. Lisinopril
• C. Irbesartan
• D. Metoprolol

Answer: (A)

Calcium channel blockers inhibit L-type calcium channels in vascular smooth muscle (and sometimes the heart), causing arteries to relax and blood pressure to fall. Amlodipine is a calcium channel blocker, specifically a dihydropyridine that mainly relaxes arterial smooth muscle to lower blood pressure. The other drugs work by different mechanisms: lisinopril is an ACE inhibitor, irbesartan is an ARB, and metoprolol is a beta-blocker. Therefore, amlodipine best fits the calcium channel blocker mechanism.