Medications and Breastfeeding

The following is a student blog post by Jessie Uchytil  

Medications and Breastfeeding- what you need to know

 One of the most common questions in my local breastfeeding support groups is “Is drug X compatible with breastfeeding?” The medical field is full of contradicting advice when medications and breastfeeding are involved. There is always worry about potential harm to baby from medications going into mother’s milk that many care providers take a “no drug is safe while breastfeeding” approach, while others say to “pump and dump” for days following a procedure. Of course there are new drugs being introduced frequently and many of them have not been tested for compatibility with breastfeeding. This paper is not meant to be a database of breastfeeding compatibility (any decisions on medication and breastfeeding should be carefully discussed with an MD). It is to understand the factors involved in milk production, how drugs enter human milk in varying amounts, and how you can find out more information about drugs so you can discuss them with some level of confidence. To understand why certain medications are safe to take while breastfeeding while others are not requires knowledge of the process of how the human body makes milk and how different medications are processed by the body.


There are several ways that drugs can find their way into breast milk. So, what are the main ways drugs do this? There are many different types of drugs and they can be processed in the body in different ways depending on their type. The following list describes the most common methods drug transfer from the mother into the milk. Note that not all drugs are processed in these ways and some drugs get into milk using more than one of these methods. It is also worth of noting that during the first few weeks of lactation the tissue of the breast is very porous and there is a greater amount of space between the cells that produce the milk which makes it easier for more drugs to pass through.

What determines how much of a drug baby is exposed to:

How the drug enters your body:

We put drugs on our skin, in our mouths; we inhale them, and even get them through IVs. The way a drug enters the body can be important. Most drugs that are applied to the skin (topically) do not enter the bloodstream easily thus do not find their way into milk in any amount that would be a cause for concern. Many inhaled drugs are the same and do not absorb easily. Oral and intravenous (through an IV) applications tend to get more significant drug amounts into the blood and milk but not always. The makeup of the drug and the way it is processed all have to do with how it gets into milk and if it stays there for long periods.

Maternal plasma level:

This is the most important factor in determining the potential of a drug transferring into milk. The higher the maternal plasma level of the drug, the more likely it is that some of the medication has made its way into the milk due to passive diffusion. To make milk the breasts must get fluid from the body. This fluid is obtained from the blood-particularly the plasma which is transferred through the milk compartments in the breasts which have a semi permeable membrane. When the maternal plasma meets the newly forming milk the components of the plasma, including the drug, want to move from an area where it is highly concentrated (the plasma) to an area where it is of lower concentration (the milk) because of the process of passive diffusion.  So if some of the drug is able to it will cross the membrane and find its way into the milk it will, but milk concentrations  will almost never become higher than the maternal plasma level either due to the diffusion process. If a mother has a high plasma level of the drug, it is likely that the drug is present in the breast milk in significant amounts for some amount of time until the concentration peaks and is then being processed out of the body, and then the drug will begin to cross the membrane again, this time leaving the milk.

Lipid solubility:

If a drug clings to fat easily, the easier it is for it to pass through the cell and store in the milk. Lipid soluble drugs can also store in the mother’s body fat and be released into the bloodstream if she burns fat.


Bioavailability is the ability for a drug to survive the digestive system and make it into the circulatory system. Many drugs are simply not able to survive the harsh environment and make it into the blood or milk in significant levels.

Molecular Weight of the medication:

The more weight to the drug, the more difficult for it to travel through the lactocytes (milk producing cells) and into milk.


The half-life of a given medication is how long it takes for the body to get rid of half of the dose. After the medicine concentration in the blood peaks it begins to process out of the body. This length of time varies and can have a big impact on how long a medication stays in the milk.


The safety of a drug while breastfeeding also has to do with the amount of milk your baby drinks. If baby is exclusively breastfeeding they will get more of the drug but if a baby is older and eating solids with only a few nursing sessions/day then they will receive significantly less of the drug.

Some people consider milk a “living” liquid since it is full of active beneficial bacteria, immune properties, and mother’s cells. Since milk welcomes so many beneficial things for baby from the mother’s body into it there is room for other substances like drugs to sneak in. If a nursing mother needs to take a medication research into the safety of the drug should be done by the mother and the physician to determine if the drug would be safe for mom and baby. Ultimately the choice is up to the mother to either withhold from the drug, to pump and remove discard the milk when the concentration in the milk is at a peak, or continue breastfeeding as normal. This choice should be an informed and educated one, not one made through generalization and guesses.  My hope is that this article breaks down the basics of drugs and breastfeeding and gives you a better understanding of the many different factors to consider when introducing a drug into your breastfeeding relationship.


For more information on safety for medications you can visit


Riordan, J. (2005). Breastfeeding and Human Lactation. Jones and Bartlett .

BIO: Jessie Uchytil is a birth worker in Terre Haute, Indiana. She grew up in Northwestern Wisconsin and Settled in Indiana and earned a Bachelor of Arts degree in music in 2012. She spent seven years in the Army National Guard, one of them in Iraq on deployment. She loves working with the people in her area helping them give birth to and raise their families.


All student article posts are the expressions of the student who wrote them. We do not take responsibility for the content, these are done as part of the educational experience and we try to encourage students to use their voice and learn to connect with clients through blogging and social media.
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