Nadolol in human serum and breast milk.

1 Simultaneous serum and milk samples were collected over a 10-day period from twelve normotensive, lactating subjects who ingested 80 mg nadolol once daily for a period of 5 days. For comparative purposes, serum samples were also collected from seven patients with a history of mild essential hypertension who ingested the same dose of nadolol for a period of 13 days. 2 In lactating subjects, steady-state serum concentrations of nadolol were attained in 3 days. Milk concentrations of nadolol were much higher than serum concentrations starting on Day 3 and throughout the remainder of the study. The mean (+/- s.e. mean) steady-state levels of nadolol in milk (356.9 +/- 40.4 ng/ml) were 4.6 times higher than the mean steady-state levels in serum (77.3 +/- 6.9 ng/ml). 3 In hypertensive patients, the mean serum concentration of nadolol 24 h after the twelfth dose was 40.3 +/- 8.2 ng/ml as compared to a mean serum concentration in lactating subjects of 40.7 +/- 3.4 ng/ml, 24 h after the fifth dose. Mean serum concentrations in hypertensive patients at 1 and 4 h after the final daily dose were not significantly different from those in lactating subjects. 4 It can be estimated that a 5 kg nursing infant would consume about 2-7% of the daily adult therapeutic dose of nadolol. The data suggest that caution should be exercised in the use of nadolol in lactating patients.