METHADONE LEVELS IN PLASMA, URINE, AND AMNIOTIC-FLUID OF METHADONE-TREATED PREGNANT RATS

Methadone was administered in the form of a slow release emulsion to n onpregnant rats and pregnant animals at early, middle, or late gestati on. Following a 48-h treatment period, plasma, urine, and amniotic flu id were analyzed for methadone and its two major metabolites using sol id-phase extraction and reversed-phase HPLC. Methadone and its primary metabolite were detected in plasma and urine of all rats with levels of both compounds comparable at all stages of gestation. No significan t difference was found for either methadone or its primary metabolite between gestation groups and nonpregnant animals. Amniotic fluid colle cted in middle and late gestation groups contained methadone and prima ry metabolite at levels similar to that of maternal plasma. These data show that methadone can be detected in plasma, urine, and amniotic fl uid following short-term treatment of pregnant rats with the opiate. M ethadone levels did not alter during pregnancy and were, in fact, simi lar to that of nonpregnant animals. These results indicate that the fe tal environment contains methadone levels comparable to that of the ma ternal circulation.