Cilazapril is a monoethyl ester, which acts as an angiotensin-converting enzyme (ACE) inhibitor. The inhibitor functions by inhibiting the the ability of ACE to cleave bonds of angiotensin I and Hip-His-Leu. It is known that the diacid form of Cilazapril is more potent that enalapril at inhibiting ACE. It is known that Cilazapril is hydrolyzed to its active acid metabolite, Cilazaprilat by non-specific esterases.