Safety in Lactation: Drugs for thromboembolic disorders

Additional information relating to breastfeeding

To be used in conjunction with individual drug entries for specific information and guidance.

Oral anticoagulants

The coumarin anticoagulants, warfarin and acenocoumarol, are considered compatible with breastfeeding. The normal practice of administering vitamin K to all neonates at birth minimises the risk of coumarin anticoagulant-induced neonatal haemorrhage

Phenindione is contraindicated because of serious adverse effects.

There is insufficient evidence for the safety of newer oral anticoagulants to confirm their safety in breastfeeding.

Parenteral anticoagulants

Heparin, low molecular weight heparins, and fondaparinux are considered compatible with breastfeeding as they are unlikely to transfer into milk in clinically significant amounts, and are not absorbed from the infant’s GI tract due to large molecular weight.

Argatroban is indicated for patients with heparin-induced thrombocytopenia requiring antithrombotic therapy. It should be avoided.

Antiplatelet drugs

The licensed indications for antiplatelet agents vary considerably. Therefore, recommendation of an alternative in breastfeeding may not be appropriate.

Aspirin, clopidogrel and prasugrel are irreversibly bound to platelets producing a prolonged antiplatelet action, although breast milk levels may be lower as a result. Dipyridamole and ticagrelor have a reversible, shorter action.

There is a theoretical risk of an association of aspirin, with Reye’s syndrome, possibly even at low doses, especially in children with a viral infection or fever.

Infants exposed to antiplatelet drugs via breast milk should be monitored for signs of bruising or bleeding.

Note: Although aspirin, clopidogrel and dipyridamole are considered to be preferred to some other antiplatelet agents, they are not without their own risks. Duration of antiplatelet effects, plasma protein binding and plasma half-lives of parent and active metabolites makes definitive guidance difficult without supporting evidence. Therefore, the use of antiplatelets in breastfeeding will depend on an individual assessment of clinical need and risk.


Fibrinolytics are unlikely to appear in breast milk in levels which could have an effect on the breastfed infant due to their short half-lives (5–46 minutes) and high molecular weights. Since they are all protein molecules, absorption from the infant’s GI tract will be negligible.

The indications for which they are used will also largely exclude breastfeeding until treatment is completed