In Vitro Drug Interactions Study of Lisinopril with Metformin

This study investigates the in vitro interactions of lisinopril with metformin which is important for the possible formulation of polypills comprising both drugs. The study was conducted using the USP apparatus II paddle method. The media used were buffer pH 1.2, 4.5, and 6.8 to simulate gastrointestinal tract pH. Lisinopril tablets (10 mg) were run in the presence of 500 mg metformin tablets and the degree of interaction was established after analyzing the dissolution samples with validated High Performance Liquid Chromatographic methods. The results indicated a statistically significant difference in the effect of lisinopril on the dissolution profile of metformin at pH 1.2, 4.5, and 6.8, with a decrease in the percentage of metformin released (p = 0.0052; p = 0.0037; and p = 0.0155, respectively). The effect of metformin on the dissolution profile of lisinopril was only statistically significant at pH 1.2 and 6.8 with an increase in the percentage of lisinopril released (p = 0.0062; p =0.0036, respectively), and no statistically significant difference at pH 4.5 (p = 0.7174).