Simultaneous liquid chromatographic determination of chloramphenicol and antiepileptic drugs (phenobarbital, phenytoin, carbamazepine, and primidone) in plasma.

A method for the simultaneous analysis of chloramphenicol and four antiepileptic drugs (phenobarbital, phenytoin, carbamazepine, and primidone) in plasma by high-performance liquid chromatography (HPLC) is described. The method involves a preliminary extraction of 0.1 ml of plasma with diethyl ether containing phenacetin as an internal standard, chromatography with a reversed-phase column with a methanol-water mobile phase, and detection by measuring ultraviolet absorbance at 210 nm. The method demonstrated sufficient precision, sensitivity, and specificity: the recoveries of the drugs were greater than 95% with the exclusion of primidone (80.3%); the maximum within-day and day-to-day coefficients of variation for all drugs were less than 5%; the lower detection limits were 0.5 microgram/ml or less for all drugs analyzed; and six other antibiotics, phenylethylmalondiamide, carbamazepine-10,11-epoxide, and chloramphenicol esters did not interfere with the analysis. The HPLC method was tested for clinical applicability by analyzing plasma samples from a volunteer who received concurrent single doses of chloramphenicol, phenobarbital, and phenytoin. This method can be used for studying drug interactions between chloramphenicol and antiepileptic drugs and for monitoring the concentrations of these drugs in plasma when administered concurrently, to prevent concentration-related side effect(s) of each drug.