Plasma disappearance of transplacentally transferred diphenylhydantoin in the newborn studied by mass fragmentography

Abstract

With the intention of studying the fate of transplacentally transferred diphenylhydantoin (DPH, phenytoin) in the newborn infant, a mass fragmentographic analytic method has been developed, in which deuterium‐labeled DPH is used as internal standard. The analytic procedure permits precise determinations of DPH in 100 µl plasma samples in concentrations down to 0.01 µg per milliliter. Seven newborn infants of epileptic mothers treated with DPH throughout the pregnancy were studied during the first 4 to 9 days of life. The rate of plasma disappearance of DPH in the newborn infants was of the same order of magnitude as previously reported in adults. The initial parts of the plasma concentration curves indicated zero‐order disappearance of DPH. Nursing did not seem to affect the rapid plasma level decline in the babies until extremely low concentrations (0.1 p.g per milliliter) were reached. The arr,wunts of unchanged drug excreted in the urine were inSignificant. It is therefore concluded that babies born by mothers treated chronically with DPH are able to metabolize this drug effectively immediately after birth.