SPECIFIC GAS-CHROMATOGRAPHIC ANALYSIS OF DIETHYLCARBAMAZINE IN HUMAN PLASMA USING SOLID-PHASE EXTRACTION

Diethylcarbamazine (DEC, 1-diethylcarbamyl-4-methylpiperazine) is an a ntiparasitic piperazine derivative used in the treatment of lymphatic filariasis. DEC-N-oxide is a major metabolite in humans which has anti filarial activity. Gas chromatographic analysis of DEC in plasma can b e complicated by the presence of the metabolite, since the thermally u nstable DEC-N-oxide is converted to a material which coelutes with DEC under the conditions of the analysis. We now report a method to separ ate DEC-N-oxide from DEC in plasma using solid-phase extraction with s ubsequent gas chromatographic analysis using a nitrogen specific detec tor. 1-Diethylcarbamyl-4-ethylpiperazine (E-DEC) was the internal stan dard. The standard curve of DEC is linear in the range of 10 to 200 ng /ml. The limit of detection is 4 ng/ml. Reproducibility at 10, 100 and 200 ng/ml concentration points of the standard curve gives coefficien ts of variation of 6.1%, 7.8% and 1.6%, respectively. Recovery followi ng solid-phase extraction is 99.3% for DEC and 94.8% for the internal standard. This sensitive and specific analytical method is suitable fo r pharmacokinetic studies of DEC. (C) 1997 Elsevier Science B.V.