Is losartan safe for use during breastfeeding?

Losartan Should Not Be Used During Breastfeeding

Losartan is not recommended for breastfeeding mothers and should be discontinued or an alternative antihypertensive agent should be selected. While there is limited human data on losartan excretion into breast milk, the FDA drug label explicitly states that significant levels of losartan and its active metabolite were present in rat milk, and recommends discontinuing either nursing or the drug 1.

Key Evidence Against Losartan Use During Breastfeeding

Direct FDA Guidance

• The FDA label for losartan states: "It is not known whether losartan is excreted in human milk, but significant levels of losartan and its active metabolite were shown to be present in rat milk. Because of the potential for adverse effects on the nursing infant, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother" 1.

Guideline Recommendations on ARBs

• The European Society of Cardiology guidelines explicitly recommend that angiotensin II receptor blockers (including losartan) should be avoided during breastfeeding, classifying them as FDA Category D drugs 2.
• This recommendation applies to the entire class of renin-angiotensin-aldosterone system inhibitors 3.

Safer Alternative Antihypertensive Options

First-Line Safe Agents for Breastfeeding

• Methyldopa, labetalol, and nifedipine-retard are considered safe during breastfeeding and can be continued from pregnancy 3.
• Amlodipine and enalapril are safe during the postpartum period with minimal excretion in breast milk 3.
• ACE inhibitors (like enalapril) have low milk-to-plasma ratios and appear safe for nursing mothers 4.
• Calcium channel blockers with low milk-to-plasma ratios are acceptable alternatives 4.

Important Caveat on Methyldopa

• While methyldopa is safe during breastfeeding, consider early withdrawal during the postpartum period as it may not be needed long-term 3.

Clinical Action Plan

1. Immediately discontinue losartan if the patient is currently breastfeeding 1.
2. Switch to a proven safe alternative such as enalapril, amlodipine, labetalol, or nifedipine based on the patient's blood pressure control needs and comorbidities 3, 4.
3. Monitor blood pressure closely during the transition period to ensure adequate control.
4. Reassure the mother that effective and safe antihypertensive options exist that are compatible with breastfeeding 4.

The lack of human data on losartan excretion into breast milk, combined with animal data showing significant transfer and the availability of well-studied safe alternatives, makes the choice clear: losartan should be avoided during breastfeeding 1, 3.