Excretion of Acebutolol and its Major Metabolite Diacetolol into Infant Blood Circulation and the Breast Milk

Acebutolol (AC) is a chiral β-adrenergic blocking drug, which is useful clinically as the racemate in treating hypertension and is metabolized to an equipotent chiral metabolite, diacetolol (DC). In this paper we report a case of a 32 year old woman who was receiving AC during her pregnancy and lactating time for management of hypertension. The maternal plasma level and breast milk as well as cord blood collected to see whether the drug is transferred to the fetus through the mother stereoselectively. A stereospecific high-performance liquid chromatographic (HPLC) assay was used to measure the enantiomeric concentrations of AC and DC. AC and DC enantiomers are stereoselectively excreted into the milk, although the concentrations of DC enantiomers were higher than those of AC. AC concentrations were very low in both cord artery and vein samples four hours after taking the drug however, the stereoselective concentrations of metabolite, DC, was found in these samples. In conclusion, AC and DC enantiomers are excreted in human breast milk in concentrations much higher than that in maternal plasma. Furthermore, DC was found in the infant’s plasma indicating that accumulation of metabolite did occur in this infant.