DETERMINATION OF CEFPODOXIME LEVELS IN CHINCHILLA MIDDLE-EAR FLUID AND PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A high-performance liquid chromatographic method has been developed to determine cefpodoxime levels in chinchilla plasma and middle ear flui d (MEF) to be used in studying otitis media. Cefpodoxime and the inter nal standard, cefuroxime, were separated on an ODS column (250 x 2.1 m m I.D., 5 mum Hypersil), using a mobile phase of 25 mM acetate buffer (pH 4.3)/15 mM triethylamine-acetonitrile (92.5:7.5, v/v). Following e lution of cefpodoxime and the internal standard, at 3.5 and 5.9 min re spectively, the acetonitrile concentration was increased to 1:1 (v/v) in a step function to elute endogenous compounds retained on the colum n. Sample preparation involved protein precipitation with acetonitrile . This fast, efficient protein precipitation procedure together with U V detection allows a quantitation limit of 50 ng/ml with a 50-mul samp le size. Recoveries (mean +/- S.D., n = 3) at 0.1 mug/ ml in MEF were 90.3 +/- 2.9% and 88.6 +/- 1.2% for cefpodoxime and cefuroxime respect ively. Recoveries (mean +/- S.D., n = 3) at 0.1 mug/ml in plasma were 72.1 +/- 7.3% and 81.1 +/- 1.1% for cefpodoxime and cefuroxime respect ively. The method was evaluated with biological samples taken from chi nchillas with middle ear infections after administering cefpodoxime pr oxetil.