Determination of erythromycin, clarithromycin, roxithromycin, and azithromycin in plasma by high-performance liquid chromatography with amperometric detection

In this study, a high-performance liquid chromatographic method was develop ed for the quantitative determination of erythromycin (EM), roxithromycin ( RXM), and azithromycin (AZM) in rat plasma with amperometric detection unde r a standardized common condition using clarithromycin (CAM) as an internal standard. This method was also proved to be applicable for the determinati on of CAM by employing RXM as an internal standard. Each drug was extracted from 150 mu l of plasma sample spiked with internal standard under an alka line condition with tert.-butyl methyl ether. The detector cell potential f or the oxidation of the drugs was set at +950 mV. The linearity of the cali bration curves were preserved over the concentration ranges of 0.1-10 mu g/ ml for EM and RXM, and 0.03-3.0 mu g/ml for CAM and AZM. Coefficients of va riation and relative error were less than 9% and +/-7%, respectively. The a nalytical method presented here was proved to be useful for the investigati on of the pharmacokinetic characteristics of EM, CAM, RXM, and AZM in rats. (C) 2000 Elsevier Science B.V. All rights reserved.