amlodipine

Amlodipine is a dihydropyridine calcium channel blocker used as an antihypertensive and antianginal medication. It is commonly prescribed in the form of amlodipine besylate (brand names include Norvasc). The drug is long-acting and typically taken once daily.

Mechanism of action: Amlodipine inhibits L-type voltage-gated calcium channels in vascular smooth muscle, reducing calcium influx. This leads to dilation of peripheral arterioles and decreased systemic vascular resistance (afterload). It also causes some coronary vasodilation, which can improve myocardial oxygen supply-demand balance. At therapeutic doses, effects on heart rate and myocardial contractility are modest.

Indications: It is approved for the treatment of essential hypertension and for chronic stable angina and vasospastic (Prinzmetal) angina. It is not indicated for acute coronary syndromes. It is frequently used in combination with other antihypertensives or antianginal agents.

Pharmacokinetics: Amlodipine has oral bioavailability in the range of about 64–90% and a long elimination half-life of roughly 30–50 hours, supporting once-daily dosing. It is highly protein-bound and undergoes hepatic metabolism primarily via the CYP3A4 system to inactive metabolites, with elimination mainly in the feces.

Contraindications and cautions: Contraindicated in hypersensitivity to amlodipine, severe hypotension, cardiogenic shock, and significant aortic stenosis. Cautions include hepatic impairment, edema, heart failure, and bradycardia. Pregnancy category C; information on use in pregnancy is limited.

Adverse effects and interactions: Common adverse effects include peripheral edema, headache, flushing, palpitations, dizziness, fatigue, and gingival hyperplasia. Drug interactions include strong CYP3A4 inhibitors (for example, ketoconazole, itraconazole, certain macrolides) and grapefruit juice, which can increase amlodipine levels; concurrent antihypertensives can increase the risk of hypotension. Rifampin and other CYP3A4 inducers may reduce its effect.