Valsartan + Hydrochlorothiazide

Valsartan is an oral medicine that belongs to a class called angiotensin receptor blockers (ARBs). It is orally active and works as a specific angiotensin II antagonist at the AT1 subtype. When angiotensin attaches to its receptors, the blood vessels narrow (vasoconstrict) and blood pressure goes up (hypertension). Valsartan blocks the angiotensin II receptor, so the vessels dilate and blood pressure falls, without any change in pulse rate. Its affinity for the AT1 receptor is much greater than for the AT2 receptor (about 20,000-fold). It does not bind or block other hormone receptors or ion channels known to be important in cardiovascular regulation. Hydrochlorothiazide is a thiazide diuretic. Thiazides act on the renal tubular mechanisms of electrolyte reabsorption and directly increase the excretion of sodium and chloride in approximately equivalent amounts. The indirect effect comes from the diuretic action of hydrochlorothiazide, which reduces plasma volume. That brings increases in plasma renin activity, aldosterone secretion and urinary potassium loss, and a decrease in serum potassium. Angiotensin II mediates the renin-aldosterone link, so giving an angiotensin converting enzyme (ACE) inhibitor together with the diuretic tends to reverse the potassium loss these diuretics cause.