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Do All Medications Pass Through Breast Milk?

breastfeeding decrease milk supply herbs medications pain medicine Oct 19, 2023
Do all medications pass through breast milk?

Medications and breast milk is an important topic for nursing mothers and health care professionals alike.

A few years ago, I saw a woman named Allison for a lactation visit. We scheduled our visit at the birthing center where she delivered her baby 2 weeks prior. She asked me to see her because she wanted to exclusively breastfeed her infant but was having trouble getting the baby to stay latched to the breast. 

I spent a couple of hours with Allison showing her how to position and latch her baby. We listened for sucks and swallows at the breast. I showed mom how to know whether her infant was eating well. We weighed the baby before and after the feeding and the infant transferred 2 ounces of milk from the breast. As a result, we were both feeling great about the encounter and Allison's potential to meet her breastfeeding goals.

Several years later, Allison signed her children up with my pediatric practice. At that time, she confessed to me that she had stopped breastfeeding her baby shortly after our lactation visit. Her milk dried up because her psychiatrist prescribed a mood stabilizing medication that affected her breast milk supply. 

Importance of Understanding Medications and Breast Milk

This story grieved me greatly as I reflected on how things could have gone differently for this mother if she had been able to advocate for herself. With better knowledge about medications and breastfeeding, potentially she could have asked for a different medication. One that did not change the course of her breastfeeding relationship so greatly.

While most medications are safe for mothers to use during breastfeeding, there are many drugs that can cause adverse effects on both breastfeeding infants or a mother's milk supply. 

In this article, we will look at medications and breast milk.

We will examine:

Medicines and Breastfeeding

Drug exposure through human milk is a concern for both health professionals and breastfeeding mothers alike. Infant exposure to medications through breast milk depends on certain medication characteristics. Whether it is a prescription drug, over the counter medication, herb or illegal drug, these characteristics affect transfer of drugs into human milk. 

We will look more closely at the effects of street drugs, alcohol, caffeine and tobacco in other articles. How do drugs affect breastfeeding?

Medication Characteristics Are Important 

  1. Oral Availability
    • If a medication is applied to the skin, injected or inhaled, it is not available through human milk to the breastfed baby.
    • Topical preparations can be absorbed into the skin and get into maternal plasma, but rarely in high enough doses to affect the baby.
    • Eye drops and nasal sprays rarely have adverse effects on breastfed babies.
  2. Molecular Size
    • Most medication transfer from mom's blood to her breast milk takes place through passive diffusion and if a medication is too large, it is unable to get into human breast milk. 
  3. Protein Binding
    • Highly protein bound medications don't diffuse into the milk. 
  4. pH
    • Breast milk is slightly acidic with a pH of 7.2.
    • This makes transfer of drugs that are weak bases easier to pass into human milk.
    • Examples of drugs that are basic are codeine, benzodiazepines and amphetamines. 
  5. Lipid solubility
    • if a drug is able to dissolve into fat (lipids) it is more likely to passively transfer into breast milk.
    • Human milk is high in fat. 

Medicines approved for Babies Are Safe

As a general rule, if a pediatrician prescribes the same medication to a baby, it is safe for breastfeeding. Infant doses obtained through breast milk are generally less than if the medicine was directly given to the baby.

This includes medications like oseltamivir (Tamiflu), short-term use of steroids, and many antibiotics.

Infant exposure to medications that are able to be prescribed to them directly are less concerning for mothers to take while breastfeeding. 

Importance of Infant Age and Medical Condition

In general, younger babies have the potential to have more adverse effects from medications that transfer into breast milk. This is because they get a relatively higher dose of the medication due to the larger volumes of breast milk that they are consuming. Infant exposure is also higher at younger ages because they are completely dependent on breast milk for their nutrition.

As a baby grows past 6 months of age, they begin to eat complementary foods. When they are beyond 9 months old,  their need for breast milk as their sole source of nutrition will start to decrease. Transfer of drugs to the infant will be lower due to less breast milk volume consumption. 

Additionally, it is important to consider premature babies and their potential for exposure to medications through mother's milk. Premature infants have the potential to receive larger amounts of drugs in their system.

Also, drug exposure through breast milk potentially causes problems for babies who have certain medical conditions. Always be sure to consult with your baby's doctor if you are concerned about a specific medication. 

Medicines with Potential to Decrease Milk Supply

There are certain medications that breast-feeding women should avoid. A lactating woman will experience a decrease in her milk supply with these drugs. Some of these medications are over the counter products while some are prescription drugs. You should always consult your health care provider before taking any new drugs during lactation.

There are also many sources listed below where you can look up medications and their effects on breastfeeding. 

  • Mood Stabilizers and Anti-Seizure Medications
    • Women with Epilepsy or Bipolar disorder may need a medication that has the adverse effect of decreasing milk supply. 
    • Mood stabilizers such as aripiprazole have been shown to decrease milk production in breastfeeding mothers.
    • Tricyclic antidepressants, psychotropic drugs and antipsychotic drugs are all medications that have the potential to interfere with milk supply. Be sure to discuss the potential adverse event of low milk supply with your physician.
  • Decongestants
    • Cold remedies that include strong antihistamines, high dose steroids and pseudoephedrine all have the potential to decrease breast milk supply.
    • In fact, in my breastfeeding medicine practice, I use pseudoephedrine (Sudafed) to decrease maternal milk supply in the setting of oversupply or weaning 
  • Oral Contraceptive Pills
    • Estrogen containing oral contraceptive pills decrease milk supply.
    • For this reason, many women opt for the mini - pill (progesterone only) or intrauterine contraceptive devices to prevent pregnancy during breastfeeding.
    • Lactational amenorrhea is also a viable birth control method in certain situations. 

Pain Medications and Mother's Milk 

Whether you had a vaginal delivery or a C-section, child birth is not pain free. Often, your OB will prescribe pain medications for you to take during your hospital stay. In addition, they will frequently send you home with a prescription. 

Different pain medications affect breastfeeding differently.

Additionally, the pain of child birth is not the only pain that you might experience during breastfeeding. For this reason, it is important to know what pain medicines are safe during breastfeeding and what should be avoided. 

Opiate Pain Medications and Breastfeeding 

When I was a newborn hospital pediatrician, I took care of newborns during the first few days of their lives. I saw what a difference pain medications made on both the mother and the baby when it came to their success with breastfeeding in the early postpartum days. 

In the age of opiates, much of post-operative and post-child birth pain is managed with these types of pain medications. As we are becoming more aware of the opiate crisis in this country, doctors are prescribing opiates less often.

On the other hand, they may prescribe them for short-term use in postpartum mothers. In general, opiate medications are safe for short-term use for breastfeeding mothers. These medications do pass into breast milk and can affect the baby. You should monitor the baby for drowsiness and rarely respiratory depression.

Potentially Dangerous Pain Medicines

Medicines that should completely be avoided in breastfeeding mothers include Tramadol and Tylenol with codeine. Both Tramadol and codeine are pro-drugs that need to be converted into active metabolites. There are several enzymes in the liver that do this work. Codeine metabolizes into morphine. 

Morphine is a powerful medication that treats pain by causing the brain to change the way you feel and respond to pain. 

Unfortunately, some people are rapid metabolizers of these pro-drugs. Their liver enzymes can rapidly change codeine into a dangerous or lethal dose of morphine. This rapid metabolism allows a large morphine dose to get to the baby through breast milk.

Tramadol has a black box warning and is contraindicated in children under the age of 12 years old. 

Safer Options for Pain

Over the counter pain medications such as acetaminophen and ibuprofen are safe ways to relieve postpartum pain for breastfeeding mothers. Ibuprofen is a nonsteroidal anti-inflammatory drug that you can use for pain as well as other forms of inflammation that may occur during breastfeeding. Mastitis, plugged ducts and nipple pain are all sources of inflammation associated with breastfeeding. 

In addition to medications, there are also many drug free ways to relieve pain. Massage, heat, stretching, warm baths or showers and rest can be alternatives to taking a pain relieving drug. 

Online Resources

There are several online resources that help guide you when it comes to medications and breast milk. It is also important to have a discussion with your health care provider if you have any specific concerns.

Trash the Pump and Dump


Hale's Medications and Mother's Milk

Infant Risk 

Safety of Medications in Pregnancy vs Breastfeeding 

If a medication is safe for you as a pregnant woman, in general it is okay to keep using it during breastfeeding. There are a few exceptions to this rule.  You might take an occasional dose of a pregnancy category C medication like pseudoephedrine (Sudafed) for congestion during pregnancy. However, you shouldn't take it while you are breastfeeding because this medication is known to decrease breast milk production. 

As always, only take a medication if you really need it. Take it for the shortest duration possible. Take the lowest dose possible. Consult with your health care provider if you have more specific questions.

Prenatal care is so important. Ask your obstetrician or midwife about medication safety during pregnancy and lactation. 

Use of Herbs and Lactation

Since ancient times, humans have used herbs and other alternative medications. They continue to grow in popularity in our current times of "natural is better." Even though herbs are natural, you still need to consider potential side effects. Additionally, consider an herb's ability to transfer into milk. 

Using Herbs to Increase Milk Supply

Certain herbs may increase milk supply.

Traditionally, we think of several herbs that show some evidence, mostly anecdotal, to increase milk supply in breastfeeding mothers. Some of these herbs also affect the breastfeeding infant.

  • Fenugreek is a herb native to the Mediterranean region, southern Europe, and western Asia.
    • It is thought to increase breast milk supply, although there is little scientific evidence that it does so.
    • In high doses, it causes a baby to be gassy  and have GI upset.
    • It also causes a maple syrup scent to both baby and mom. Be sure that your pediatrician knows if you are using this herb. We often worry about a metabolic condition if we catch a whiff of maple syrup on a baby. 
  • Blessed Thistle is a flowering plant with sharp prickles on the stems and leaves.
    • It's native to the Mediterranean region.
    • It has traditionally been used to relieve digestive issues, but in large quantities it can actually cause GI disturbances.
    • There are a few small studies that show no harm to breastfeeding babies, but no good evidence that it truly increases breast milk supply
  • Goat's Rue - a plant that is used to make medications.
    • A chemical in this plant (galegine) is what scientists use to make the drug metformin. This medication is used to lower blood sugar in diabetic patients.
    • In breastfeeding, goat's rue is thought to increase milk supply by increasing insulin sensitivity. Insulin resistance is thought to play a role in milk production.
    • Goat's Rue got its name from the fact that it increased milk production in goats. Read more interesting facts here

Can Herbs be Harmful?

Certain herbs decrease milk supply. As a physician, I use peppermint or sage tea to decrease milk supply in mothers with oversupply. Additionally, in large doses, eating peppermint candies decrease breast milk production.

Herbs and other supplements are not regulated by the FDA in this country. This means that there is no oversight for production and manufacturing of these compounds. As a result, you cannot be completely sure that you are taking a safe compound. Be sure to use a reputable site if you choose to use herbs anytime, but especially during breastfeeding. 

Resources for safe use of herbs in Lactation

National Center for Complementary and Integrative Health 

Natural Medicine Database


Medications and breast milk causes stress in both health care professionals as well as lactating women. Thankfully, most medications are safe for use by breast-feeding women. Hopefully, this article helped you to find peace with this topic.

© 127 Pediatrics; October 2023

This article is for informational purposes only and should not be construed as medical advice.

Dr. Wadley, 127 Pediatrics
Andrea Wadley, MD, IBCLC

Dr. Andrea Wadley is the owner, pediatrician, and breastfeeding medicine specialist for 127 Pediatrics. She has an established house-calls only pediatric practice in Colleyville, TX. She is also the owner and operator of the 127 Pediatrics Online Breastfeeding Medicine and Education Center.


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