Amlodipine is the USA's #5 most prescribed drug — 68.7M Rx/yr. This 2026 complete guide covers the L-type calcium channel mechanism, why ankle swelling hits 10–30% and the ACE inhibitor fix that millions miss, the FDA simvastatin 20mg cap interaction, grapefruit CYP3A4, the 35–50 hour half-life advantage, a 5-class antihypertensive comparison table, and the ACCOMPLISH trial amlodipine + ACE inhibitor superiority evidence.