Atenolol pharmacokinetics and excretion in breast milk during the first 6 to 8 months postpartum

Abstract

The objectives were to evaluate the time course for atenolol pharmacokinetics in lactating women postpartum and to quantify atenolol plasma concentrations in the women's 3- to 4-month-old nursing infants. Data were collected during 1 dosing interval from lactating women treated with atenolol for therapeutic reasons, at 2 to 4 weeks (n = 32), 3 to 4 months (n = 22), and 6 to 8 months (n = 17) postpartum. A single blood sample was collected from 15 nursing infants (3-4 months of age) of the mothers participating in the study. At 2 to 4 weeks, 3 to 4 months, and 6 to 8 months postpartum, atenolol infant doses, relative to the mother's weight-adjusted dose, were 14.6% ± 7.6%, 8.3% ± 5.2% and 5.9% ± 2.9%, respectively. Over this time, maternal atenolol pharmacokinetics did not change to a clinically significant extent. Atenolol concentrations were below assay quantification limits (<10 ng/mL) in the plasma of all 3- to 4-month-old nursing infants studied. These findings support the careful use of atenolol during breastfeeding, because in the vast majority of healthy, term infants, atenolol concentrations will be too low to be clinically relevant. Premature infants and those with kidney disease require further study. Infant exposure depends on maternal dose and decreases during the first 6 to 8 months postpartum.

Figure 1

Amount of atenolol excreted daily in breast milk for 2–4 weeks (n=32), 3–4 months (N=22), and 6-8 months (n=15) postpartum. Error bars indicate standard deviations. Numbers in the bars indicate the number of subjects in each dose and study day group.

Figure 2

Correlation between atenolol dose (A) or atenolol maternal plasma AUC (B) and atenolol AUC in breast milk for 2–4 weeks (n=32), 3–4 months (N=22), and 6-8 months (n=15) postpartum.

Figure 3

Average atenolol concentration–time profiles in plasma and breast milk (n=15) for subjects treated with atenolol twice daily (adjusted to 50 mg/day) 2–4 weeks postpartum (A), 3–4 months postpartum (B), and 6-8 months postpartum (C). Error bars represent standard deviations.