Simultaneous Quantification of Glibenclamide, Simvastatin, and Quercetin by Using LC-UV Method and Its Application to Pharmacokinetic Study in Rats

A sensitive, precise, and simple LC method for the simultaneous quantification of glibenclamide, simvastatin, and quercetin in rat plasma has been developed and validated. The chromatographic separation was achieved on a cyano column (250？mm × 4.6？mm, 5？μm) maintained at room temperature, using isocratic elution with methanol？:？acetonitrile？:？10？mM potassium dihydrogen orthophosphate, pH adjusted to 4.5 with o-phosphoric acid (8？:？32？:？60, v/v) and detected using UV-VIS detector. Plasma samples were deproteinated with 0.1% perchloric acid and acetonitrile for extraction of the glibenclamide, simvastatin, and quercetin which resulted in their high recoveries. LC calibration curves based on the extracts from the rat plasma were linear in the range of 50–1000？ng？mL？1 for all the three drugs. The limit of quantification was 50？ng？mL？1. The described method was successfully applied to study the pharmacokinetics of glibenclamide, simvastatin, and quercetin following oral administration, in combination to Sprague-Dawley rats. 1. Introduction Diabetes mellitus is one of the most prevalent metabolic syndrome which on progression leads to many secondary complications. One of the major clinical manifestations associated with Type II diabetes is hyperlipidemia which subsequently predisposes the patient to cardiovascular diseases and many other complications [1, 2]. Amongst the various lipid lowering drugs, statins are the most widely accepted therapy [3]. However, with respect to the dose level, efficacy, and tolerability, simvastatin has been found to be the most beneficial. Illingworth et al. (2001) suggested that simvastatin led to a greater increase in HDL cholesterol and apo A-I levels in hypercholesterolemic patients as compared to atorvastatin [4]. Apart from controlling lipid levels, effective management of blood glucose level is also primary concern for the diabetic patients, which generally requires a combination of oral antihyperglycemic drugs. Glibenclamide, a second generation sulfonylurea, has been widely used alone or in combination due to its ability to effectivly control the blood glucose level [5]. Thus a patient with Type II diabetes and hyperlipidemia has to undergo multiple therapies simultaneously which may include concomitant therapy of drugs like glibenclamide and simvastatin. However, one major concern is the low oral bioavailability of simvastatin (<5%) due to its rapid metabolism by CYP3A4 isoenzymes [6]. Thus, it becomes important to improve its oral bioavailability for attaining better therapeutic efficacy at a lower dose which may also