About captoprilsa specific competitive angiotensin-converting enzyme (ace) inhibitor, antihypertensive.smechanism of action of captoprilsit is an angiotensin converting enzyme inhibitor prevents the conversion of angiotensin-1 to angiotensin-2 and abolishes the pressor actions of angiotensin. it decreases aldosterone secretion, sodium and water retention, and total peripheral resistance, leads to fall in bp. the arterioles dilate and the compliance of larger arteries is increased. both systolic and diastolic bp is lowered. it has no effect on cardiac output and cardiovascular reflexes. and there is little dilatation of capacitance vessels- so postural hypotension is not a problem. the drug does not compromise renal, cerebral, and coronary blood flow. bp lowering depending up on sodium status and renin angiotensin activity. so greater fall in bp occurs in reno vascular accelerated and malignant hypertension. the drug also increases plasma kinin levels and potentiate the hypotensive a