Pharmacokinetic and Bioavailability Studies of Commercially Available Simvastatin Tablets in Healthy and Moderately Hyperlipidemic Human Subjects

Abstract

Simvastatin, an analogue of Lovastatin, is a HMG.CoA reductase inhibitor. It is widely used in the treatment of hyperlipidemia and coronary heart disease (CHD) with low incidence of myopathy and rhabdomyolysis. As these diseases may alter the pharmacokinetics of drugs, the present study was aimed to elaborate the variation in the pharmacokinetics and bioavailability of simvastatin in local healthy and moderately hyperlipidemic population. Open, single dose and parallel design was applied to study. A total of 36 male volunteers were used for healthy and moderately hyperlipidemic groups (n = 18 for each) in this study on the basis of screening procedures, body chemistry and physical examination. Simvastatin 40 mg tablets (Saista 40, Bosch, Pakistan) were administered to over-night fasted volunteers. Blood samples were collected before dosing (zero time) and at regular intervals of time. The plasma samples were processed through a liquid-liquid extraction procedure and assayed by using HPLC consisting reversed phase C18 column (ZORBAX, 4.6 x 150 mm, 5 µm), UV detector set at 238 nm. The mobile phase consisted of the mixture of 0.025 M sodium dihydrogen phosphate (pH 4.5): acetonitrile (35: 65, v/v) which was pumped at a flow rate of 1.5 mL.min-1. The retention time of simvastatin was 7.5 minutes. The plasma drug concentration-time profiles of both groups were found significantly (P < 0.05) identical. The data was analyzed by using Kinetica® version 4.4 according to non-compartment model of pharmacokinetic analysis. There was statistically no significant (P > 0.05) difference between the values of following pharmacokinetic parameters in healthy and hyperlipidemic volunteers i.e. Cmax, tmax, AUC0-∞, AUMC0-∞, MRT, t1/2, Clt and Ke. This study confirmed no significant (P > 0.05) difference in pharmacokinetics and bioavailability parameters after the administration of a single oral dose of 40 mg simvastatin (cholesterol lowering drug) to healthy and moderately hyperlipidemic volunteers.