Losartan (50mg) + Amlodipine (5mg) + Hydrochlorothiazide (12.5mg) (Medical Monograph)

Overview

A triple-drug, fixed-dose combination (FDC) antihypertensive therapy containing an angiotensin II receptor blocker (ARB), a dihydropyridine calcium channel blocker (CCB), and a thiazide diuretic. This combination provides synergistic blood pressure lowering through complementary mechanisms, targeting the renin-angiotensin-aldosterone system (RAAS), vascular smooth muscle calcium channels, and sodium/fluid balance. It is indicated for patients whose hypertension is not adequately controlled on dual therapy. The FDC improves compliance by reducing pill burden.

The combination exerts a multi-pronged attack on hypertension. Losartan selectively and competitively antagonizes the AT1 receptor, blocking the vasoconstrictor and aldosterone-secreting effects of angiotensin II. Amlodipine inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle, causing peripheral arterial vasodilation and reduced peripheral vascular resistance. Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule of the nephron, increasing excretion of sodium, chloride, and water, thereby reducing plasma volume.