[A quantitative gaschromatographic method for the determination of p-chlorophenoxyisobutyric acid (clofibrinic acid) in human plasma (author's transl)].

The report describes a sensitive and selective GLC-method for the plasma level estimation of p-chlorophenoxyisobutyric acid (CPIB), the biologically active metabolite of clofibrate. After addition of an internal standard substance the acid is extracted and converted to its methylester by diazomethane. Following oral administration of equimolar doses of clofibrinic acid and clofibrate (445 and 500 mg, respectively) to 4 normal volunteers plasma concentrations could be measured for 72 h. A comparison of different pharmacokinetic parameters indicated that the two compounds gave almost identical absorption profiles in respect of CPIB. CPIB disappeared from plasma with a mean half-life of 17.6 h.