Is metoprolol (beta-blocker) safe to use during lactation in a patient with hypertension or heart failure?

Metoprolol Safety in Lactation

Metoprolol is safe to use during lactation and is specifically recommended by major cardiology guidelines as a preferred beta-blocker for breastfeeding mothers with hypertension or heart failure. 1, 2

Guideline-Based Recommendations

Beta-1 selective agents like metoprolol are explicitly preferred over non-selective beta-blockers during lactation. 1 The European Society of Cardiology specifically states that β1-selective drugs (i.e., metoprolol) should be preferred for heart failure treatment in breastfeeding women, while atenolol should not be used. 1

The 2022 AHA/ACC/HFSA Heart Failure Guidelines recommend metoprolol as the preferred beta-blocker during lactation, with specific instructions to monitor neonatal heart rate. 1 This recommendation applies to both hypertension and heart failure management in the postpartum period.

Safety Profile and Infant Exposure

Infant exposure to metoprolol through breast milk is negligible. 3, 4 Key safety data includes:

• Plasma concentrations of metoprolol in breastfed infants are negligible or below the limit of detection 3
• Relative infant exposure through breast milk is less than 1.0% of the maternal weight-adjusted dose 4
• The milk-to-plasma ratio ranges from 2.0 to 3.1, but absolute amounts transferred remain clinically insignificant 3

Metoprolol's high protein binding minimizes transfer into breast milk, making it safer than other beta-blockers like atenolol. 2

Practical Dosing Considerations

If timing of nursing is a concern, exposure can be further minimized by avoiding breastfeeding within 3-4 hours after dose intake. 3 However, this is generally unnecessary given the already minimal infant exposure.

During pregnancy, metoprolol clearance increases substantially (up to 3-fold in late pregnancy), but this normalizes postpartum. 4 Standard adult dosing is appropriate during lactation without need for adjustment.

Required Monitoring

Newborns should be supervised for 24-48 hours after delivery to exclude hypoglycemia, bradycardia, and respiratory depression. 1 After this initial period, ongoing monitoring of the breastfed infant should focus on:

• Heart rate changes 1, 2
• Weight gain patterns 1, 2
• Feeding behavior 2

Clinical Decision Algorithm

1. For heart failure in lactating women: Continue or initiate metoprolol as part of guideline-directed medical therapy 1
2. For hypertension in lactating women: Metoprolol is an acceptable option, though calcium channel blockers (nifedipine, amlodipine) are generally preferred as first-line agents 5, 2, 6
3. If beta-blocker is specifically indicated: Metoprolol is the preferred choice over atenolol or other beta-blockers 1, 2

Critical Pitfalls to Avoid

Never use atenolol during lactation—it concentrates more heavily in breast milk and poses greater risk to the infant. 1, 5, 2 Atenolol should be avoided due to risk of fetal growth restriction and higher infant exposure.

Do not discontinue necessary beta-blocker therapy solely due to breastfeeding—metoprolol's safety profile supports continuation. 1 The benefits of treating maternal cardiovascular disease outweigh the minimal theoretical risks to the infant.

Ensure ACE inhibitors, ARBs, and aldosterone antagonists are avoided during pregnancy but can be added postpartum if needed for heart failure, as these have separate lactation safety profiles. 1