To nurse when receiving acebutolol: is it dangerous for the neonate?

The concentrations of acebutolol and of its main active metabolite diacetolol in milk and plasma were studied in 7 hypertensive mothers treated with acebutolol, a cardioselective beta-adrenoceptor blocking agent. Clinical monitoring on their newborn babies was also done, as well as measurement of plasma level of the drug in them. The ratio between milk and plasma concentrations ranged from 1.9 to 9.2 for acebutolol and from 2.3 to 24.7 for diacetolol, and in any given milk sample, the diacetolol concentration was always higher than that of acebutolol. In a newborn infant, plasma concentrations of the two transplacentally acquired substances was raised when breast feeding started and remained high. Clinical signs of pharmacological beta-blockade were observed. Evaluation of the iatrogenic risk shows that pharmacologically active amounts of acebutolol might be received by a neonate if the daily maternal dosage exceeds 400 mg/day and/or renal function in the mother is impaired.