ENAP-CO

Enalapril is hydrolysed via hepatic CES 1 to the active metabolite enalaprilat, which acts as an ACE inhibitor. ACE is a peptidyl dipeptidase which catalyses the conversion of angiotensin I to the vasoconstrictor substance angiotensin II and hence inhibition of ACE results in decreased plasma angiotensin II. This also leads to increased plasma renin activity and decreased aldosterone secretion. The mechanism of action of enalapril is therefore primarily via the suppression of the RAAS. However, ACE is identical to kininase II, and so enalapril may also exert its effects by blocking the degradation of bradykinin, a potent vasodepressor peptide.

Hydrochlorothiazide is a diuretic with antihypertensive properties. It acts by inhibiting the renal tubular re-absorption of sodium and chloride ions, which are excreted with an accompanying volume of water. Potassium excretion is also promoted.