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 (discoloration of the fingers and toes due to spasm of blood vessels). All calcium channel blockers relax smooth muscles in the wall of arteries which leads to reduction in blood pressure and some calcium channel blockers also slow down the heart rate and reduce the force of heart contraction which can be useful in certain arrhythmias, such as atrial fibrillation, but must be avoided in heart failure.
Amlodipine, felodipine, lacidipine and lercanidipine are examples of CCBs acting purely on blood pressure whereas verapamil and diltiazem are also influence heart rate and cardiac contractility. CCBs are normally 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.