[Determination of amoxicillin in human plasma by high performance liquid chromatography and its pharmacokinetics]

A rapid and sensitive assay for amoxicillin in human plasma has been developed using reversed phase high performance liquid chromatography. Plasma samples were prepared for analysis by addition of internal standard (tinidazole) followed by protein precipitation with HClO4. A YWG C18H37 column as stationary phase and a 0.033 mol.L-1 phosphate buffer (pH 7.2)--methanol mixture (85:15) as mobile phase were used with the UV detector set at 229 nm. The calibration curve was linear in the range from 0.2 microgram.ml-1 to 20.0 micrograms.ml-1 with gamma > 0.999. The analytical recovery of amoxicillin from plasma was > 86.7%. The relative standard deviations for within-day and between-day were < 5.48% and < 8.29%, respectively. Following oral administration of 500 mg in human volunteers, the peak levels of amoxicillin in plasma averaged 6.88 +/- 2.25 micrograms.ml-1 at 84.4 +/- 21.1 min. The mean half life time for amoxicillin was 62.8 +/- 14.6 min.