LISINOPRIL AN OVERVIEW

Abstract

Lisinopril is an oral long-acting angiotensin converting enzyme inhibitor. It is a lysinederivative of Enalprilate and has structural similarity with its substrate. It differs from captopril by lacking the sulfhydryl group [1,2]. Lisinopril is chemically described as (S)-1-[N2-(1carboxy-3-phenylpropyl)-L-lysyl]-Lproline dihydrate. Its empirical formula is C₂₁H₃₁N₃O₅.2H₂O.The present study was aimed at developing a simple, sensitive, precise and accurate HPLC method for the estimation of Lisinopril from bulk samples and tablet dosage forms. A non-polar C8 analytical chromatographic column was chosen as the stationary phase for the separation and determination of Lisinopril. Mixtures of commonly used solvents like water, methanol and acetonitrile with or without buffers in different combinations were tested as mobile phases. The choice of the optimum composition is based on the chromatographic response factor, a good peak shape with minimum tailing. A mixture of buffer and methanol in the ratio of 35:65 v/v was proved to be the most suitable of all the combinations since the chromatographic peak obtained was well defined, better resolved and almost free from tailing. The retention time of Lisinopril was found to be 2.29 min. The linearity was found satisfactory for the drug in the range 20.0-60.0 μg/mL (Table 1.4). Precision of the method was studied by repeated injection of tablet solution and results showed lower % RSD values (Table 1.5-1.7). This reveals that the method is quite precise. The percent recoveries of the drug solutions were studied at three different concentration levels. The percent individual recovery and the % RSD at each level were within the acceptable limit (Table 1.8). This indicates that the method is accurate. The absence of additional peaks in the chromatogram indicates non-interference of the commonly used excipients in the tablets and hence the method is specific. The deliberate changes in the method have not much affected the peak tailing, theoretical plates and the percent assay. This indicates that the present method is robust (Table 1.9). The system suitability studies were carried out to check various parameters such as theoretical plates and tailing factor (Table 1.10). The lowest values of LOD and LOQ as obtained by the proposed method indicate that the method is sensitive (Table 1.11). The solution stability studies indicate that the drug was stable up to 24 hours (Table 1.12). The forced degradation studies indicate that the drug was stable in stability studies (Table 1.13).