Is Atenolol safe while breastfeeding?

Effects on the breastfed infant

A study of mothers taking beta-blockers during nursing found a numerically, but not a statistically significantly increased number of adverse reactions in those taking any beta-blocker. Although the ages of infants were matched to control infants, the ages of the affected infants were not stated. Of 13 mothers taking atenolol, one reported lethargy in her breastfed infant; she was also taking other unspecified drugs for hypertension.[ 18 ] Cyanosis, bradycardia and hypothermia occurred in a 5-day-old infant probably because of atenolol in breastmilk. Her mother was taking atenolol 50 mg twice daily. Symptoms continued until day 8 when breastfeeding was discontinued.[ 9 ] No difference between resting and crying heart rates were observed in 22 breastfed (extent not stated) infants aged 3 to 4 months whose mothers were taking atenolol in an average oral dosage of 49 mg daily. This finding indicated that the infants were experiencing no beta-adrenergic blockade from atenolol in breastmilk.[ 3 ] Other authors have reported 15 infants aged 3 days to 2 weeks exposed to atenolol in breastmilk with no signs of adverse effects. Maternal dosages were 50 or 100 mg daily.[ 5 - 7 , 13 , 15 , 16 , 19 ]

Effects on milk supply

One unusual case of oligomenorrhea, hyperprolactinemia and galactorrhea was reported in a 38-year-old woman who had been taking atenolol for about 18 months. Prolactin values returned to normal within 3 days of discontinuation of atenolol. Galactorrhea slowly lessened and disappeared one month after atenolol discontinuation.[ 20 ]

Levels in milk

The excretion of beta-adrenergic blocking drugs into breastmilk is largely determined by their protein binding. Those with low binding such as atenolol at 10% are more extensively excreted into breastmilk. Accumulation of the drugs in the infant is related to the fraction excreted in urine. With 85% renal excretion, atenolol presents a high risk for accumulation in infants, especially neonates. Maternal Levels. The time of the peak milk level of atenolol varied between 2 and 8 hours after the dose in 5 women.[ 4 - 6 ] In one woman a peak level of 1.6 mg/L occurred 4 hours after a single 50 mg dose.[ 5 ] After a single dose of 100 mg of atenolol in 4 women 4 to 12 days postpartum, peak milk levels ranged from 1.4 to 2.1 mg/L.[ 6 ] In 6 women taking atenolol 100 mg daily, two milk samples were taken in one day at unstated times after the dose. Milk levels ranged from 0.025 to 2.1 mg/L (average 0.7 mg/L).[ 7 ] In a study of 5 early postpartum women, single milk levels taken 2 hours after a dose ranged from 0.38 to 1.04 mg/L (average 0.63 mg/L) with a dosage of 100 mg daily.[ 8 ] Because of the single early sample taken, these probably do not represent the peak milk levels in these women. Another woman taking atenolol 50 mg twice daily had an atenolol milk levels of 469 mcg/L 1.5 hours after a dose which probably does not represent the peak milk level.[ 9 ] It is estimated that a fully breastfed infant would receive between 5.7 and 19.2% of the maternal weight-adjusted dosage of atenolol.[ 10 ] Nine women taking atenolol in dosages ranging between 25 and 200 mg daily (average not stated) in 2 divided doses had milk atenolol levels averaging 464 mcg/L at 2 hours after a dose. There was a 53% coefficient of variation in the levels measured, in part due to the wide range of dosages.[ 11 ] Breastfeeding women taking oral atenolol for hypertension were studied during 3 time periods: 2-4 weeks postpartum, 3-4 months postpartum and 6-8 months postpartum. Seventeen women were e

Alternatives LactMed lists

• Propranolol
• Labetalol
• Metoprolol