A pregnant woman was acutely referred to the maternity ward with hypertension due to eclampsia, wit

Fråga: A pregnant woman was acutely referred to the maternity ward with hypertension due to eclampsia, with systolic blood pressure 200 and diastolic 120. She was treated with Trandate (labetalol) intravenously 400 mg in 500 ml glucose 45 ml per hour. The child was delivered after slightly less than 24 hours of treatment of the mother with labetalol. The child showed decreased tonus and hypoglycaemia 1.1 mmol/L. After treatment with intravenous glucose a level of 3.9 mmol/L blood glucose was attained. The question is: what is known about the toxicity, kinetics and possibility of antidote treatment to the child when the mother has been treated with labetalol?

Sammanfattning: The alpha-beta-blocker labetalol is frequently used to treat pregnancy-induced hypertension in pregnant women. It is apparently accompanied by an increased risk of hypoglycaemia in the child. Other symptoms of beta-blockade may also be seen after treatment of the mother before giving birth.

Svar: Labetalol is a combined alpha- and betareceptor blocker. The physiological antidote would therefore be epinephrine. Prenalterol is another conceivable antidote. Documentation for the use of these compounds in neonates is lacking.

The drug easily passes across the placenta and cord serum concentrations range between 40 and 80 per cent of the maternal blood concentration (1,2). The half-life of labetalol in normal adults is approximately four hours. In the newborn the half-life may be significantly prolonged, up to 24 hours (3). Breast-milk concentrations were up to 2.6 times plasma concentration. However, the maximal concentrations in the plasma of breast-fed children never exceeded the trough concentration of the mother.

The effect of labetalol on the child seems to be mainly a hypoglycaemic reaction as a result of high doses of labetalol. In one controlled clinical trial comparing labetalol and hydralazine, blood glucose levels were significantly lower in the labetalol group at 6 hours of age (4). In a study aimed at studying adverse effects of labetalol, hypoglycemia was significantly more frequent in the children of labetalol-treated women than in the children of women treated for pregnancy-induced hypotension with other antihypertensives (5). In that study higher doses of labetalol were noted in mothers of children with symptomatic hypoglycaemia than in the mothers of asymptomatic children. There is also a case report where a child of a mother treated with labetalol reacted with bradycardia, hypoglycaemia and hypotension. In this child the plasma concentration rose steadily over the first three days of life (6).