A simple, rapid, sensitive and relatively specific reverse phase HPLC assay procedure for glibenclamide in rat and human plasma is described. The method employs considerably smaller sample volume (0.2 mi) and a single step extraction with dichloromethane. A relatively high degree of sensitivity (detection limit of the assay was 20 ngml(-1)) was obtained by using fluorescence detection at excitation and emission wavelengths of 308 and 360 nm, respectively. The mean percentage recovery of the drug in the concentration range of 30-120 ng was 100.6% while the between-day coefficient of variation for the same concentration range was 7.29%. The assay procedure offers a much better degree of resolution for the glibenclamide peak than was previously reported. This was achieved through the use of a chromatographic column with a finer packing material (Novapak C-18, 4 pm) and by selecting the ideal composition, pH and elution rate of the mobile phase - methanol: 0.05 M potassium dihydrogen phosphate (61:39 v/v, pH 4 and pumped at 1.2 ml.min(-1)). It is hoped that this micro assay technique will find wider application in both clinical and subclinical pharmacokinetic studies involving glibenclamide.
