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Atenolol Pregnancy and Breastfeeding Warnings

Atenolol is also known as: Tenormin

Atenolol Pregnancy Warnings

Atenolol crosses the placental barrier and appears in cord blood. Administration of atenolol in the second trimester of pregnancy has been associated with the birth of infants that are small for their gestational age. In addition, some data have shown a significantly decreased fetal heart rate and significantly decreased mean birth weight of infants whose mothers were taking atenolol relative to those taking acebutolol or pindolol. Case reports of profound beta-blockade in neonates of mothers who were taking atenolol are reported. Because of this, observation of affected neonates for bradycardia and hypotension is recommended for 48 hours postpartum. The results of one study indicate that maternal renal function, mean cardiac output, and heart rate are significantly increased, while mean total peripheral resistance is significantly decreased during the second and third trimesters as compared to 3 months postpartum.

Atenolol has been assigned to pregnancy category D by the FDA. Animal studies have revealed evidence of dose-related embryotoxicity and fetotoxicity. Atenolol has been used during human pregnancy (starting in the second trimester) with evidence of lower birth weight and preterm (less than 37 weeks) delivery. Neonates born to mothers who are receiving atenolol at parturition may be at risk for hypoglycemia and bradycardia. Atenolol should only be given during pregnancy when there are no alternatives and benefit outweighs risk.

Atenolol Breastfeeding Warnings

Atenolol is excreted into human breast milk at a ratio of 1.5 to 6.8 when compared to the concentration in plasma. Neonates born to mothers who are receiving atenolol and are breast-feeding may be at risk for hypoglycemia and bradycardia. The manufacturer recommends that caution be used when administering atenolol to nursing women.

Milk atenolol levels may be four times higher than maternal serum levels. One case of bradycardia, peripheral cyanosis, and hypothermia is reported in a nursing infant whose mother was taking atenolol 50 mg orally every 12 hours. The authors calculated that the atenolol exposure to the nursing infant was 9% of the mother's daily dose. Because of this, observation of nursing infants for bradycardia and hypotension is recommended during breast-feeding. In addition, neonates born to mothers who are breast-feeding may be at an increase risk for hypoglycemia. Premature infants or infants with impaired renal function may be more at risk to develop side effects.

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