Lisinopril is an oral long-acting angiotensin converting enzyme inhibitor. Lisinopril, a synthetic peptide derivative, is chemically described as (S)-1-[N2-(1-Carboxy-3- phenylpropyl)-L-lysyl]-L-proline dihydrate. Its empirical formula is C21H31N3O5•2H2O.

Lisinopril is a white to off-white, crystalline powder, with a molecular weight of 441.53. It is soluble in water and sparingly soluble in methanol and practically insoluble in ethanol.