Losartan

**Semantic type:** Organic Chemical|Pharmacologic Substance

**Definition:** A non-peptide angiotensin II antagonist with antihypertensive activity. Upon administration, losartan and its active metabolite selectively and competitively blocks the binding of angiotensin II to the angiotensin I (AT1) receptor. This blocks the vasoconstricting and aldosterone-secreting actions of angiotensin II, leading to a decrease in blood pressure. Angiotensin II, formed from angiotensin I by angiotensin-converting enzyme (ACE), stimulates the adrenal cortex to synthesize and secrete aldosterone, which decreases the excretion of sodium and increases the excretion of potassium. Angiotensin II also acts as a vasoconstrictor in vascular smooth muscle.

**Synonyms:** - 2-Butyl-4-chloro-1-[[2'-(1H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl]-1H-imidazole-5-methanol - LOSARTAN - losartan