Calcium channel blockers (CCBs) or calcium antagonists are used to treat hypertension (high blood pressure), angina (chest pain due to narrowings, blockages, or spasms of coronary arteries), migraine, and Raynaud’s disease (discolouration of the fingers and toes due to spasm of blood vessels). All calcium channel blockers relax smooth muscles in the arteries wall, leading to a reduction in blood pressure and some calcium channel blockers also slow down the heart rate and reduce the force of heart contraction. That can be useful in certain arrhythmias, such as atrial fibrillation, but must be avoided in heart failure.

Amlodipine, felodipine, lacidipine, nifedipine, and lercanidipine are examples of CCBs acting purely on blood pressure (dihydropyridine CCBs), whereas verapamil and diltiazem are also reducing heart rate and cardiac contractility. CCBs are usually well tolerated but some patients experience ankle swelling (particularly with amlodipine) and constipation (verapamil). Other less common side effects include headache, drowsiness, rash, and facial flushing. Whilst on CCBs, patients need to avoid grapefruit juice because of interaction which potentiates the effect of CCBs.