Distribution of Pethidine and Chlorpromazine in Maternal, Foetal and Neonatal Biological Fluids

Abstract

EVIDENCE for placental transfer of drugs was obtained in 1885 when Preyer¹ observed mydriasis in newborns whose mothers had received belladonna during labour. Since then analgesia has been recognized as a considerable problem in obstetrics, for the opiates and other allied and synthetic narcotics administered during labour have respiratory depressant effects on the foetus. While the search for optimum analgesia with minimum adverse effects on the foetus continues, pethidine, first introduced in 1940², is still widely used—usually with other drugs. Comprehensive reviews of the literature^3,7 relating to placental transfer of pethidine and its suitability for obstetrical use reveal wide discrepancies in clinical observations and a lack of precise experimental results. To provide quantitative data which may be correlated with systematic clinical observations, I examined the distribution of pethidine and chlorpromazine and a wide range of their metabolites in amniotic fluid, maternal and foetal plasma and maternal and neonatal urine.