Effect of Hibiscus sabdariffa (Calyxes) water extract on the in vitro availability of lisinopril

Background: The concurrent use of herbs and drugs for the treatment of various ailments is a common practice amongst patients; a practice that could result in drug-herb interaction.Objectives: This study is aimed at evaluating the effects of Hibiscus sabdariffa on in vitro availability of lisinopril.Method: The availability of lisinopril alone and in presence of Hibiscus sabdariffa calyxes water extract was determined using dissolution apparatus (BP, 2013) set at 50 rpm and 37 °C in 900 mL of three different dissolution media [0.1 M HCl (simulated gastric pH), phosphate buffers pH 6.8 (simulated intestinal pH) and phosphate buffers pH 7.4 (simulated blood pH)]. Samples (5 mL) were withdrawn from the media at 5, 10, 15, 30, 45, and 60 min and replaced immediately with the same medium. Each sample was analysed for the lisinopril content released using UV spectrophotometry at 215, 210 and 215 nm in 0.1 M HCl, phosphate buffers pH 6.8 and phosphate buffers pH 7.4 respectively.Results: Results showed that the media has no effect on the dissolution profile of lisinopril alone, however, it was observed that 89.40 (lisinopril alone) and 92.62 % (lisinopril in the presence of Hibiscus sabdariffa) was released in simulated gastric pH. The corresponding contents of lisinopril observed in simulated intestinal pH were 89.40 and 92.51 %, while in simulated blood pH 89.40 and 91.95 % of lisinopril was released. The presence of Hibiscus sabdariffa significantly (p < 0.05) increased the in vitro availability of lisinopril in all the media.Conclusion: The results of this study suggest that coadministration of lisinopril with Hibiscus sabdariffa could enhance its in vitro availability consequent to the increased dissolution of lisinopril in simulated gastric, intestinal and blood pH.Keywords: Lisinopril, Interaction, Hibiscus sabdariffa, dissolution