Simultaneous determination of clarithromycin and 14(R)-hydroxyclarithromycin in plasma and urine using high-performance liquid chromatography with electrochemical detection.

A sensitive method for the simultaneous high-performance liquid chromatographic determination of clarithromycin and its active metabolite in plasma and urine is described. Alkalinized samples were coextracted with an internal standard and analyzed on a C8 column using electrochemical detection. Recoveries were greater than or equal to 85% and consistent. Standard curves for plasma were linear in the range 0-2 micrograms/ml for both compounds (r greater than 0.99), with limits of quantification of approximately 10.03 micrograms/ml (0.5-ml sample). Within-day and day-to-day precision were good, with coefficients of variation mostly within +/- 5%; accuracy for both compounds were routinely within 90-110% of theoretical values. Standard curves for urine were linear in the range 0-100 micrograms/ml with limits of quantification of 0.5 micrograms/ml (0.2-ml sample). Urine assays also had similar within-day and day-to-day precisions and accuracy.