Breastfeeding and Medications

Over the years, far too many mothers have been wrongly told they had to stop breastfeeding because they must take a particular drug. The decision about continuing breastfeeding when the breastfeeding parent takes a drug, for example, is far more involved than whether the baby will get any in the milk. It also involves taking into consideration the risks of not breastfeeding, for the breastfeeding parent, the baby and the family, as well as society. And there are plenty of risks in not breastfeeding, so the question essentially boils down to: Does the addition of a very small amount of medication to the breastfeeding parent’s milk make breastfeeding more hazardous than formula feeding? The answer is almost never. Breastfeeding with a little drug in the milk is almost always safer. In other words, being careful means continuing breastfeeding, not stopping.


Remember that stopping breastfeeding for a week or more or even only a couple of days may result in permanent weaning as the baby may then not take the breast again. On the other hand, it should be taken into consideration that some babies may refuse to take the bottle completely, so that the advice to stop is not only wrong, but often impractical as well. On top of that it is easy to advise the breastfeeding parent to pump milk while the baby is not breastfeeding, but this is not always easy in practice and the breastfeeding parent may end up painfully engorged.


When the baby is a toddler, something more needs to be taken into account. A major issue that so many people, especially physicians, seem to forget, is that a baby this age may be very emotionally upset, distraught, to be forced from the breast. Many babies of this age and older love breastfeeding, are very attached to breastfeeding and depriving them of it can cause them to cry for hours on end, for days on end. To force them to stop, is cruel and needs to be taken into account when advising the breastfeeding parent.



Help with breastfeeding


Medications in Breastmilk:


Most drugs appear in the milk, but usually only in tiny, even minuscule amounts. Although a very few drugs may still cause problems for infants even in minuscule doses, this is not true for the vast majority. Breastfeeding parents who are told they must stop breastfeeding because of a certain drug should ask the physician to make sure of this by checking with reliable sourcesNote that the CPS (in Canada) and the PDR (in the USA) are not reliable sources of information about drugs and breastfeeding.  These “resources” are merely a compilation of the information provided by the drug manufacturers who are more interested in their medical legal liability than the interests of the mother and baby.  Their policy is essentially “We can’t be held responsible if we advise the breastfeeding parent to interrupt breastfeeding”.  But if there is a real concern in the rare case, the breastfeeding parent should ask the physician to prescribe an alternate medication that is acceptable during breastfeeding. One of the rare cases is the use of letrozole (Femara) to induce ovulation. Although not contraindicated during breastfeeding and like all drugs appearing only in tiny amounts in the milk, it is better not to use in the breastfeeding mother.  However, there are alternatives to induce ovulation that are safe.


Why do most drugs appear in the milk in only small amounts? Because what gets into the milk depends on the concentration of drug in the breastfeeding parent’s blood, and the concentration in the breastfeeding parent’s blood is often measured in micro- or even nano-grams per millilitre (millionths or billionths of a gram), whereas the parent takes the drug in milligrams (thousandths of grams) or even grams. Furthermore, not all the drug in the breastfeeding parent’s blood can get into the milk. Only the drug that is not attached to protein in the blood can get into the milk. Many drugs are almost completely attached to protein in the breastfeeding parent’s blood. Thus, the baby is not getting amounts of drug similar to the breastfeeding parent’s intake, but almost always, much less on a weight basis. For example, in one study with the antidepressant paroxetine (Paxil), the mother got over 300 micrograms per kg per day (the usual dose being 20 to 50 mg per day), whereas the baby got about 1 microgram per kg per day.


Most Drugs Are Safe If:


They are commonly prescribed for infants. The amount the baby would get through the milk is much less than he would get if given directly.


They are considered safe in pregnancy. This is not always true, since during the pregnancy, the pregnant parent’s body is helping the baby get rid of drug. Thus it is theoretically possible that worrisome accumulation of the drug might occur during breastfeeding when it wouldn’t during pregnancy (though this is rare).  However, if the concern is for the baby’s being exposed to a drug, say an antidepressant, then the baby is getting exposed to much more drug at a much more sensitive time during pregnancy than during breastfeeding.  Recent studies about withdrawal symptoms in newborn babies exposed to SSRI type antidepressants (Paxil, for example) during the pregnancy somehow managed to imply that breastfeeding should not be allowed because of the tiny amounts of drug in the milk as if this type of problem requires a mother not to breastfeed. In fact, you cannot prevent these withdrawal symptoms in the baby by breastfeeding, because the baby gets so little in the milk. In fact at least one study suggests that breastfeeding decreases the withdrawal symptoms in the baby, though I suspect it’s more the skin contact with the breastfeeding parent that decreases the symptoms, not the tiny amounts of drug in the milk. 


They are not absorbed from the stomach or intestines. These include many, but not all, drugs given by injection. Examples are gentamicin (and other drugs in this family of antibiotics such as tobramycin), heparin, interferon, local anaesthetics, omeprazole.  Omeprazole (Losec, Prilosec) and other drugs of this family of proton pump inhibitors such as lansoprazole (Prevacid), pantoprazole (Tecta) and others are interesting because they are destroyed very quickly by stomach acid. During the manufacture of the drug, a protective layer is added to these drugs to prevent their destruction by stomach acid and such drugs are absorbed into the breastfeeding parent’s body. However, when the baby gets the drug (in minuscule amounts incidentally) there is no protective layer on the drug, so it is immediately destroyed in the baby’s stomach.


They are not excreted into the milk. Some drugs are just too big to get into the milk. Examples are heparin, interferon, insulin, infliximab (Remicade), etanercept (Enbrel) and a host of new monoclonal antibodies (or biologicals). Indeed, even if any of the previously mentioned drugs did get into the milk (they don’t) they would be destroyed in the baby’s stomach.


The Following Are A Few Commonly Used Drugs Considered Safe During Breastfeeding:

Acetaminophen (Tylenol, Tempra), alcohol (in reasonable amounts), aspirin (in usual doses, for short periods). Most antiepileptic medications, most antihypertensive medications, tetracycline, doxycycline codeine, nonsteroidal antiinflammatory medications (such as ibuprofen), prednisone, thyroxin, propylthiouracil (PTU), methimazole, warfarin, tricyclic antidepressants, sertraline (Zoloft), paroxetine (Paxil), other antidepressants, metronidazole (Flagyl), omeprazole (Losec), Nix, Kwellada.


Note: Though generally safe, fluoxetine (Prozac) has a very long half-life (stays in the body for a long time).  Thus, a baby born to a parent on this drug during the pregnancy, will have large amounts in his body, and even the small amount added during breastfeeding may result in significant accumulation and side effects. These are rare, but have happened. There are two options that you might consider:


  • Stop the fluoxetine (Prozac) for the last 4 to 8 weeks of your pregnancy. In this way, you will eliminate the drug from your body and so will the baby. Once the baby is born, he will be free of drug and the small amounts in the milk will not usually cause problems and you can restart the fluoxetine (Prozac).
  • If it is not possible to stop fluoxetine (Prozac) during your pregnancy, consider changing to another drug that does not get into the milk in significant amounts once the baby is born. Two good choices are sertraline (Zoloft) and paroxetine (Paxil).


Medications applied to the skin or inhaled (for example, drugs for asthma) or applied to the eyes or nose, are almost always safe for breastfeeding.


Drugs for local or regional anaesthesia are not absorbed from the baby’s stomach and are safe. Drugs for general anaesthesia will get into the milk in only tiny amounts (like all drugs) and are extremely unlikely to cause any effects on your baby. They usually have very short half-lives and are eliminated extremely rapidly from your body. You can breastfeed as soon as you are awake and up to it.


Immunizations given to the breastfeeding parent do not require breastfeeding to be stopped. On the contrary, the immunization will help the baby develop immunity to that immunization, if anything gets into the milk. In fact, most of the time nothing does get into the milk, except, possibly some of the live virus immunizations, such as German Measles. And that’s good, not bad.


X-rays and scans. Ordinary X-rays do not require a breastfeeding parent to interrupt breastfeeding even when used with contrast material (example, intravenous pyelogram). The reason is that the material does not get into the milk, and even if it did it would not be absorbed by the baby. The same is true for CT scans and MRI scans. You do not have to stop for even a second. 


What About Radioactive Scans? 

We do not want babies to get radioactivity, but we rarely hesitate to do radioactive scans on them. When a breastfeeding parent gets a lung scan, or lymphangiogram with radioactive material, or a bone scan, it is usually done with technetium (though other materials are possible).  Technetium has a half-life (the length of time it takes for ½ of all the drug to leave the body) of 6 hours, which means that after 5 half-lives it will be gone from the breastfeeding parent’s body (do the math). Thus, 30 hours after injection, all of it will be gone (well 98% will be gone) and the breastfeeding parent can breastfeed the baby without concern about the baby getting radiation. But does all the radioactivity need be gone? After 12 hours, 75% of the technetium is gone, and the concentration in the milk very low. I think that waiting 2 half-lives is enough, for a material such as technetium. But: Not all technetium scans require stopping breastfeeding at all (HIDA scan, for example).  It depends on which molecule the technetium is attached to.  In the first few days, there is very little milk (though there is enough).  In this situation it would be unnecessary for the mother to stop breastfeeding after a lung scan, for example.  However, one of the most common reasons to do a lung scan is to diagnose a blood clot in the lung.  This can now be done better and faster with CT scan, which does not require interrupting breastfeeding for even 1 second.


If you decide that interruption of breastfeeding is the best course to follow, (though we emphasize again that it is almost never necessary), then express milk for several days in advance (if you have advance warning about the test) and this can be fed via cup for a few days. Then while not breastfeeding, express your milk but don’t throw away the milk.  The radioactive tracer that is present in the milk decays and the radiation is gone in 5 half-lives.  So, even for I¹³¹ used in thyroid scans (see below), the radioactivity of the iodine will be gone in 5 half-lives, so the milk can be used in 6 to 8 weeks (the half-life of I¹³¹ is about 8 days). Only occasionally is a radioactive scan so urgent that it cannot be delayed for a few days.  In fact, there are other ways of diagnosing thyroid problems than with radioactive iodine.  And better ways of treating hyperthyroidism than radioactive iodine.


Thyroid scans are different. Radioactive iodine (I¹³¹) is concentrated in milk and will be ingested by the baby and it will go to his thyroid where it will stay for a long time. This is definitely of concern. So, the breastfeeding parent will have to stop breastfeeding? No, because often the test does not need to be done at all. Differentiating postpartum thyroiditis from Graves’ Disease (the most common reason for doing the scan in breastfeeding parents) does not require a thyroid scan. Get more information from the clinic.  If a scan needs to be done, it is possible to do a thyroid scan I¹²³ which requires stopping for only 12 to 24 hours, depending on the dose given or technetium (see above).  Don’t forget to express milk in advance so the baby can get it instead of formula. 



The information presented here is general and not a substitute for personalized treatment from an International Board Certified Lactation Consultant (IBCLC) or other qualified medical professionals.

This information sheet may be copied and distributed without further permission on the condition that you credit International Breastfeeding Centre, it is not used in any context that violates the WHO International Code on the Marketing of Breastmilk Substitutes (1981) and subsequent World Health Assembly resolutions. If you don’t know what this means, please email us to ask!


©IBC, updated July 2009, July 2017


Questions or concerns?  Email Dr. Jack Newman (read the page carefully, and answer the listed questions).
Make an appointment at the Newman Breastfeeding Clinic.