Is telmisartan (angiotensin II receptor antagonist) HCTZ (hydrochlorothiazide) safe during breastfeeding?

Telmisartan/HCTZ and Breastfeeding

Telmisartan/HCTZ should not be used during breastfeeding and must be discontinued before nursing begins. 1

FDA Drug Label Guidance

The FDA explicitly states that women should not breastfeed during treatment with telmisartan due to potential serious adverse reactions in the breastfed infant, including hypotension, hyperkalemia, and renal impairment. 1 This recommendation is based on:

• No available human data on telmisartan presence in breast milk, effects on the breastfed infant, or effects on milk production 1
• Animal data showing telmisartan present in rat milk at concentrations 1.5 to 2 times those in plasma from 4-8 hours after administration 1
• Known class effects of angiotensin receptor blockers (ARBs) causing serious neonatal complications, including a documented case of neonatal acute renal failure following maternal telmisartan exposure 2

Guideline Consensus on ARBs During Lactation

Multiple authoritative guidelines uniformly recommend avoiding ARBs during breastfeeding:

• The JNC 7 hypertension guidelines explicitly state that "ACEIs and ARBs should be avoided on the basis of reports of adverse fetal and neonatal renal effects" 3
• The 2011 ESC cardiovascular disease in pregnancy guidelines recommend discontinuing ARBs before breastfeeding begins 3
• The 2022 AHA/ACC/HFSA heart failure guidelines note that ACE inhibitors (enalapril or captopril preferred) may be appropriate during breastfeeding with neonatal monitoring, but do not extend this recommendation to ARBs 3

Hydrochlorothiazide Considerations

HCTZ poses an additional concern during lactation:

• Diuretics can suppress lactation by reducing milk volume 3
• The 2020 ESC peripartum hypertension guidelines state that diuretics (including HCTZ) "may reduce milk production and are generally not preferred in breastfeeding women" 3
• While furosemide may be appropriate with neonatal follow-up, HCTZ is not specifically endorsed for lactation 3

Safer Alternative Antihypertensive Options

If blood pressure control is needed during breastfeeding, consider these well-studied alternatives:

• ACE inhibitors: Enalapril or captopril are preferred, with neonatal weight monitoring 3
• Beta-blockers: Metoprolol is preferred, with neonatal heart rate monitoring 3
• Methyldopa: Has an established safety record during lactation 3
• Labetalol: Acceptable alternative with high protein binding 3, 4
• Calcium channel blockers: Nifedipine has favorable data 3

These alternatives have documented low milk-to-plasma ratios and extensive clinical experience without reported infant harm. 4

Clinical Management Algorithm

1. Discontinue telmisartan/HCTZ before initiating breastfeeding 1
2. Switch to a compatible antihypertensive (preferably enalapril, captopril, or metoprolol) with multidisciplinary consultation including neonatology/pediatrics teams 3
3. Monitor the infant for appropriate parameters based on the chosen medication (weight for ACE inhibitors, heart rate for beta-blockers) 3
4. Avoid diuretics if possible to prevent lactation suppression, but furosemide may be used if essential with close neonatal follow-up 3

Critical Pitfalls to Avoid

• Do not assume ARBs are safe simply because ACE inhibitors can be used during lactation—these are distinct drug classes with different lactation safety profiles 3
• Do not continue telmisartan based on the absence of reported cases, as this reflects lack of data rather than evidence of safety 1
• Do not overlook HCTZ's effect on milk production, which can compromise breastfeeding success independent of infant safety concerns 3