Calcium channel antagonists

Mechanism: calcium channel antagonists block L-type voltage-gated calcium channels, reducing calcium entry into vascular smooth muscle (vasodilatation) and into cardiac myocytes and nodal tissue (negative inotropy and negative chronotropy/dromotropy).

Classification: Dihydropyridines — amlodipine, nifedipine, felodipine, nitrendipine, lercanidipine: predominantly vascular selectivity, potent arterial vasodilators, minimal effect on the AV node. Non-dihydropyridines — verapamil (phenylalkylamine, most cardioselective) and diltiazem (benzothiazepine, intermediate): act directly on the AV node, slowing conduction.

Why they suit older patients: they are peripheral vasodilators that maintain coronary blood flow, and their potency increases with age — a consequence of reduced reflex tachycardia and reduced myocardial contractility in the elderly. They are especially effective in isolated systolic hypertension.

Indications: hypertension (particularly ISH and in older and Black patients), stable angina (added when symptoms persist despite long-acting nitrates and beta blockers), rate control in atrial fibrillation and supraventricular tachycardia (non-dihydropyridines), Prinzmetal/vasospastic angina, and Raynaud phenomenon.

Choice by ventricular function (a key examination point): in stable ischaemic heart disease, rate-limiting agents (diltiazem, verapamil) may be used if left ventricular function is normal, whereas dihydropyridines (amlodipine, felodipine) should be used when ventricular function is impaired.

Evidence: calcium channel blockers reduced stroke incidence in older patients with isolated systolic hypertension (Syst-Eur, Staessen 1997) and are superior to other classes for stroke prevention, but they do not significantly reduce the risk of heart failure — for which diuretics are superior.

Adverse effects (dihydropyridines): headache and flushing, ankle oedema (dose-dependent, not diuretic-responsive — best managed by dose reduction or by adding an ACE inhibitor/ARB), sodium retention, reflex tachycardia (short-acting agents), gum hyperplasia, and postural hypotension.

Adverse effects (non-dihydropyridines): constipation (prominent with verapamil and a real problem in older patients), bradycardia, AV block, and negative inotropy — they may precipitate or worsen heart failure and are contraindicated in HFrEF and in acute pulmonary oedema.

Interactions and cautions: combining verapamil or diltiazem with a beta blocker carries a substantially increased risk of bradycardia, heart block and asystole, particularly in older people; both are CYP3A4 inhibitors and raise levels of statins, digoxin and carbamazepine. Essentials lists among its "Don'ts": do not use short-acting calcium channel antagonists for long-term therapy of hypertension.

Practical prescribing in geriatrics: prefer long-acting once-daily dihydropyridines; start at low dose; review ankle oedema and constipation at each visit; check for bradycardia if combined with a beta blocker; and remember that calcium channel blockers are among the drugs that can cause bradycardia and are a recognised secondary cause of hyponatraemia-associated hypotensive states. Latest Updates and Current Practice Update (concise) 2025 ACC/AHA and 2024 ESC hypertension guidelines retain dihydropyridine calcium channel blockers as one of the four first-line classes, and both now strongly favour their use within single-pill combinations (typically with an ACE inhibitor/ARB and/or a thiazide-like diuretic) as initial therapy. The ACE inhibitor + amlodipine combination is preferred over amlodipine + diuretic for reducing ankle oedema and, from the ACCOMPLISH trial, for cardiovascular outcomes — a practical point not covered in the textbooks. Calcium channel blockers remain the safest antihypertensive class in advanced chronic kidney disease and in patients in whom hyperkalaemia limits RAAS blockade, which is common in the multimorbid elderly.