• The National Institute for Health and Clinical Excellence (NICE) reviewed the available evidence on use of antihypertensive drugs in breastfeeding women [National Collaborating Centre for Women's and Children's Health, 2010]. The studies identified measured non-clinical endpoints, such as secretion of the drug in the mother's milk or detection of the drug in the infant's plasma. No studies were found on whether antihypertensive drugs taken while breastfeeding had adverse effects on the infants.

Use of labetalol, nifedipine, and methyldopa

• NICE concluded that:
• The drugs mostly likely to be used by breastfeeding women seem to be suitable: labetalol, nifedipine, and methyldopa.
• However, NICE does not recommend the use of methyldopa in the postnatal period due to the risk of depression. This view conflicts with advice from the Medicines and Healthcare products Regulatory Agency (MHRA), which recommends methyldopa as the drug of choice during breastfeeding [MHRA, 2009].

Use of atenolol and metoprolol

• NICE commented that there are no known adverse effects.

Use of angiotensin-converting enzyme (ACE) inhibitors

• There is conflicting advice about the use of ACE inhibitors:
• NICE recommends that if ACE inhibitors are needed, then captopril or enalapril should be used because of the quality and quantity of associated safety data.
• However, the MHRA recommends that ACE inhibitors should not be used by breastfeeding mothers in the first few weeks after delivery. This is because, although amounts of the drug transferred to the infant by breastfeeding are unlikely to be clinically relevant, data are insufficient to exclude the possibility of profound hypotension in the infant. The MHRA considers that pre-term infants may be at particular risk. The MHRA suggests that the use of captopril, enalapril, or quinapril may be considered in older infants who are being breastfed.

Use of angiotensin-II receptor antagonists (AIIRAs)

• Both NICE and the MHRA agree that AIIRAs should not be used as there are no data on their use and their effects on breastfeeding infants.

Use of amlodipine

• NICE found insufficient evidence of safety and, therefore, does not recommend the use of amlodipine.

Use of diuretics

• NICE make no statement regarding the use of diuretics for treating hypertension in a woman who is breastfeeding.
• Although the amount of bendroflumethiazide excreted in breast milk is too small to be harmful, care is needed that the diuresis does not cause dehydration, leading to inhibition of breastfeeding. However, this is less likely if a low dose of 2.5 mg daily is used [LactMed, 2007].