Using medications while breastfeeding

Dr. Koren is the founder and director of the Motherisk Program and professor of Paediatrics, Pharmacology, Pharmacy, and Medical Genetics at the University of Toronto. He is also the Richard and Jean Ivey Chair in Molecular Toxicology in the Schulich School of Medicine, at The University of Western Ontario, where he holds the rank of professor in Medicine and Paediatrics.


When you need to take a medication while breastfeeding, you may be concerned about how it may affect your baby. The good news is that only a very few number of drugs pose a risk to breastfed babies. In general, cancer drugs, drugs of abuse and radiopharmaceuticals should not be taken, while most other medications, including over-the-counter drugs for cold and flu, are okay to take.

Breastfeeding is best for providing all necessary nutrients to infants for the first 6 months of life. Use of medication while lactating, however, complicates the decision to breastfeed. Fortunately, most drugs are okay to take while breastfeeding and do not pose a risk to infants. Here, we discuss which medicines are compatible and incompatible with breastfeeding, in light of the practice guidelines of the Motherisk Program.

Seasonal over-the-counter medications

Cold remedies such as acetaminophen (e.g. Tylenol), the Non-Steroidal Anti-inflammatory Drugs (NSAIDs) including ibuprofen (e.g. Advil), naproxen and similar medications, antihistamines and sympathomimetic drugs used in nose drops, are all okay to take while breastfeeding.

Drugs generally considered incompatible with breastfeeding

Anti-cancer drugs. Anti-cancer drugs used in chemotherapy are generally considered incompatible with breastfeeding because even very low levels of exposure can be toxic to the baby.

Antiepileptics. Only a few of the old anticonvulsants are excreted in high concentrations in breast milk. Phenobarbital, ethosuximide and primidone might result in substantial exposure to the infant. Infants exposed to phenobarbital should be monitored closely because their blood levels might approach therapeutic levels, sedation has been observed and there is potential for withdrawal upon weaning.

Drugs of abuse. Generally speaking, all drugs of abuse should be avoided by nursing women. Alcohol may be associated with decreased milk intake by infants, altered sleep patterns and slower neurologic development. If you drink alcohol, you could withhold breastfeeding temporarily (about 2 to 3 hours per drink) to ensure alcohol levels in the milk have diminished. Motherisk has developed a chart to guide you on how long to withhold breastfeeding, based on how much you drank and your body weight.

Radiopharmaceuticals. Some diagnostic medical tests require the use of radioactive compounds called radiopharmaceuticals. If you need a test that requires radiopharmaceuticals, you may need to temporarily stop breastfeeding because radioactivity sometimes stays in breast milk for hours or even days. Before procedures like this, breast milk may be pumped and frozen to be given to infants while breastfeeding is temporarily withheld. In addition, mothers should pump and discard their breast milk while the radioactivity is still present, in order to preserve milk production. You should be given individualized recommendations, depending on the particular radiopharmaceutical agents used for your test. Consulting with a nuclear medicine physician or with Motherisk can help you and ensure peace of mind.

Other medications. A few medications, such as the cardiac drug amiodarone or the drug lithium for bipolar disorder, may not be safe in every case. Patients who take these medications need close follow up of the baby.


Only a few drugs pose a risk to infants through breast milk. This is reassuring for both breastfeeding mothers and healthcare providers faced with weighing the risks and benefits of certain medications. Contact the Motherisk Program for specific information on any short-term and long-term medications you may need to take during breastfeeding.


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