Stress Degradation of Lisinopril Dihydrate in Different Aqueous Media

Abstract

Lisinopril is an antihypertensive drug from the ACE inhibitor group. It is often used in practice and, in oral administration is characterized by very low percentage of resorption (~25%). Therefore, it is important to ensure the stability of this drug, since any degradation leads to a decrease in the percentage of resorption and an increased risk of sub-dosage of patients. In accordance with modern trends of pharmaceutical analysis, the chemical stability of lisinopril under the influence of various aqueous media was tested: distilled water, 0.1M HCl, 0.1M and 0.01M NaOH and 3% hydrogen peroxide solution. In order to clearly define the effect of elevated temperature on the stability of this drug, tests were carried out at 25 °C and 50 °C. High-pressure liquid chromatography was used as the method for stability testing. The obtained results clearly define that lisinopril is the most sensitive to hydrolysis in the base environment, where at 25 °C, in the first minute, it degrades ~100%. In this paper, kinetic parameters (degradation constant rate, half-life of degradation, order kinetics, and activation energy) were also determined, which enabled clear definition of the stability and identification of degradation products of lisinopril under the influence of various stress agents. In the degradation of lisinopril in neutral and acidic medium, impurity D is identified as the main degradation product.