What Are the Dangers of Drug Use When Breastfeeding?

Using Drugs While Breastfeeding Can Have Dire Consequences

Woman holding baby

In general, breastfeeding is considered to be the best way to feed your baby during their first year of life. However, if you need to take medications or have an addiction to substances like recreational drugs or alcohol, you could harm your body. 

It's important to be upfront with what medications or substances you use with your doctor. Your physician can help you decide what to do. They will need to consider the following two questions in making their recommendations to you:

  1. How much of the drug is excreted in your breastmilk, and
  2. What is the risk of adverse (or harmful) effects on your baby?

To answer the first question, how much of the drug is excreted in your breastmilk, the physician will have to consider certain physical characteristics of the drug, which in turn affects the "milk-to-plasma drug concentration ratio," which relates to the proportion of the drug that is in your breastmilk. However, this ratio varies over time, so it is not an absolute measure. Also, this ratio is meaningless unless other factors are taken into account.

The actual level of exposure of the drug to the baby can be estimated by assuming the baby will drink a specific amount of milk per day, although in reality, this varies. This is compared with the therapeutic dose of the drug, and the "rate of clearance" of the drug by the baby is also taken into account -- the lower the level of clearance, the higher the baby's exposure to the drug.

For most drugs, it is not known at what level a dose will produce no effects on the baby. Therefore, a level of 10% of the therapeutic dose for infants (or the equivalent dose for adults, adjusted by body weight) is used. So if the dosage the baby will receive is less than 10%, the drug exposure will generally be considered unimportant, although there are some exceptions.

Obviously, these calculations become a lot more difficult if you are using street drugs, because the concentrations of active ingredients are largely unknown. But your physician will be able to discuss the best course of action for you and your baby, including a safe plan for reducing and coming off drugs. There is more information on street drugs as well as legal and prescription drugs below.

Answering the second question, what is the risk of adverse (or harmful) effects on your baby, is more difficult because so little is known about the effects of drugs on infants via breastmilk. It would be unethical and no one would volunteer for a controlled study that might put their baby at risk by deliberately giving them drugs. However, there is some research available on babies whose mothers were already taking drugs while breastfeeding.


Research shows that babies exposed to cocaine through breastmilk may experience extreme irritability, tremulousness, vomiting and diarrhea.


Read the full article on Marijuana and Breastfeeding

Marijuana ingested through breastmilk may cause delays in motor development.


Methadone withdrawal can be experienced by babies who ingest it through breastmilk, severely enough to cause death. However, some reports suggest that up to 20mg per day may be taken by the mother while breastfeeding, while others suggest up to 80mg per day. Methadone concentrations should be monitored in both the mother's breastmilk and the baby's blood if the mother is taking above 20mg of methadone a day. Buprenorphine has been suggested as a safer alternative.


Read the full article on Alcohol and Breastfeeding

Drinking alcohol while breastfeeding is not recommended, so if you have successfully abstained from alcohol while pregnant, don't start drinking again while breastfeeding. If you have consumed alcohol during pregnancy, your child is at risk of Fetal Alcohol Spectrum Disorder (FASD), so talk to your doctor as soon as possible about referring your child for early intervention, which may help your child with learning and development.

Research shows that babies exposed to alcohol through breastmilk have increased sleep (please don't be tempted to use this as a way of getting your baby off to sleep), the baby may have reduced milk intake, and the mother may have reduced milk ejection. In general, alcohol is harmful to the brains and bodies of people regardless of their age, so bear this in mind and act responsibly.


There are many painkillers on the market, ranging from over-the-counter to prescription drugs. Some are known to increase the risk of neurobehavioral depression in babies exposed through breastmilk. Talk to your physician about the safest alternatives for you, and consider non-drug alternatives to pain relief, at least while breastfeeding.


Caffeine is one of our most widely accepted drugs, so little is written about the effects on babies. However, caffeine intake through breastmilk does increase irritability, and animal studies suggest decreased brain weight and alterations in brain development, learning and memory in offspring exposed to caffeine through breastmilk.


Causing nicotine-induced toxicity in babies exposed to nicotine in the breastmilk, reduced milk volume in the mother, and early weaning, smoking has also been associated with decreased fertility in female mice offspring exposed to nicotine through breastmilk. Most importantly, if you are smoking around your baby, you are increasing their risk of conditions such as SIDS and asthma, regardless of whether you are breastfeeding. Quitting smoking is strongly advisable.

Final Thoughts

Remember, the current trend is to breastfeed to provide your baby with the best possible start in life. But be honest with yourself about whether it will really provide the best start.

Discuss your alcohol and drug use in detail with your doctor, and follow their advice to the letter, especially regarding detox.


Eskenazi, B. "Caffeine - Filtering the Facts" N Engl J Med 343:1348. 1999.

Hampton, T. "Smoking and Pregnancy" JAMA 298:2474. 2007.

Ito, S. "Drug Therapy for Breastfeeding Women" N Engl J Med 343:118-126. 2000.

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