Breastfeeding Chemistry Part 1: Medications, Alcohol, and Breastfeeding

Most people are very careful about what they eat, drink, and what medications they take during pregnancy. After the baby is born, a breastfeeding parent will usually continue to be cautious. So it’s important to know what is OK to use when breastfeeding.

It’s true that there are many substances out there that shouldn’t be used when breastfeeding. People hear horror stories about decades ago when medications were routinely prescribed to pregnant women which caused severe and terrible birth defects. You hear about how you have to “pump and dump” if you drink alcohol while you’re breastfeeding. It’s true that mistakes were made in the past, but it’s also true that there are a lot of myths and rumors circulating around this topic.

What Medications are Safe to Take while Breastfeeding?

It might be surprising to hear that most medications are safe to take with breastfeeding. The benefits of breastfeeding can also usually outweigh the risks that taking certain medications might add. Always be sure to check with your Lactation Consultant (IBCLC) and your Primary Care Provider when considering medication options.

There is an excellent database powered by The National Center for Biotechnology Information (NCBI), which is part of the United States National Library of Medicine, a branch of the National Institutes of Health. It’s called the LactMed Database. This is a great educational resource about how different substances affect lactation. It can’t exactly give recommendations, but it has a lot of information about how the substances are studied in relation to breastfeeding.

Hale’s Medications & Mothers’ Milk reference book is the leading resource for updated recommendations regarding breastfeeding and medications. The book is updated regularly, but it is big and pricey. They also have an app that requires a subscription to search the entire database, but might be less expensive than the book, if you just need it for a short amount of time.

Of course, it’s important to discuss any medication or substance use with your care providers! An Internationally Board Certified Lactation Consultant (IBCLC) is well-educated about medications and lactation and will use these resources to help advise their clients and offer information about medication safety related to breastfeeding. They will also urge you to have a conversation with your primary care provider before continuing with medication use or changes.

The Science of Medication in Breastmilk

It might surprise you that there are A LOT of medications that are safe to use while breastfeeding. There is some interesting science behind what makes medication more or less safe. To be honest, I wasn’t a big fan of my high school chemistry class BUT stay with me because this is some pretty cool chemistry.

First, I think it’s important to know how the milk gets stuff from YOUR body. Good things like antibodies and proteins from your blood (and sometimes bad things and medications too) get through by passing through the walls of our tiny blood vessels and into the alveolar cell which makes milk.

Molecules have to pass through both walls of those cells to get to the baby. RIGHT AFTER the baby is born (4-10 days), there are big gaps between these cells. That gap gets a lot smaller when those cells begin to swell later on. So, in those first 10 days of life, all the good stuff your baby needs from you can get through more easily, but so can other things. Care providers will be more cautious about what is prescribed during that window. After that, medications are chosen to be safe or unsafe based on some interesting chemistry.

Some drugs don’t even get into the milk.

1. The amount of a drug that gets into milk depends a lot on how much is in the mother’s blood plasma. Most drug molecules do end up there, BUT inhaled medications or drugs given in the nose usually don’t! So that’s why a breastfeeding mother might be given certain medication in an inhaled or intranasal version.
2. The molecular weight of the drug molecule matters. A heavyweight molecule will be too big to get through the cell walls and into the milk!
3. If the drug molecule likes to bind to proteins, it’s a lot LESS likely to get into the breast milk. The drug molecule is floating around in the blood plasma, but then it sees a BIG protein and is attracted to it. When the drug attaches to the protein, it can’t get into the breastmilk because the whole thing is too big to fit through the gap. So, it stays in the maternal bloodstream but doesn’t get into the milk at all.
4. The half-life of the medication might be very short. The half-life is how long a drug stays “alive” or active. If a drug has a very short half-life, by the time the molecules get to the milk ducts, they are starting to break down so the amount that gets into the milk is even less. If there’s a time-lapse before the baby needs a feed, it breaks down even more. So, even if these are small enough to get in, they break down quickly and very few molecules get into the baby.

Some drugs will not be prescribed because they build up in the milk TOO MUCH.

1. Can the drug be “ion trapped”? Milk has lower pH. Drugs that have a lower pH or are IODINATED, get “trapped” in the milk. For that reason, iodine can really build up in milk. I like to imagine that both the milk and the drugs are “sticky”, so they stay together. If a drug molecule is more “greasy” or slippery, it can get out (this is not science, it’s just my way of picturing something complicated!) So, drugs that can get trapped should be avoided.
2. If the drug is “lipid (fat) soluble”, it will stay in the breast milk at higher levels. Milk is fatty too, so that makes sense, right? Lipid-soluble drugs should be avoided.
3. Drugs with a very small molecular weight can easily get through and into the milk. These drugs should be avoided. Alcohol is one of those.
4. Drugs that are very active with a long half-life should probably be avoided.

What happens if the drug DOES get into the milk?

The baby drinks the milk and the drug. As a general rule, less than 1% of the dose of medication you take will make its way into the milk and into the baby. This might not be a problem in some cases.

1. For many drugs, such a small amount won’t have a negative impact on the baby.
2. Some drugs have poor “oral bioavailability”. That means it goes into the baby’s digestive system but gets easily broken down by the baby’s stomach acid and doesn’t enter the bloodstream. OR sometimes a drug doesn’t get absorbed into the bloodstream well when it’s taken with calcium-rich foods (MILK!). So if the baby is having a milk meal, the drug won’t get absorbed much or at all. Also, there are many drugs that are not absorbed well through the digestive tract, and will just pass through.

Breastfeeding and Alcohol

What about alcohol? Do you have to “pump and dump?”

There is some controversy and misinformation about what it means to drink alcohol if you’re breastfeeding. “Pump and dump” means you pump out your milk and throw it away after you’ve been drinking. The thought is that there is alcohol in that milk and you should throw it out so you’re not feeding your baby a milk cocktail.

This is not true. Alcohol DOES transfer from your bloodstream into the milk, but it doesn’t build up and STAY there. It moves back and forth between your blood and your milk supply to find a balance.

If you have a lot of alcohol in your bloodstream, there will be more in the milk. As long as you have alcohol in your bloodstream, all your new milk will have alcohol in it too, so pumping before the alcohol has left your bloodstream is sort of pointless. BUT if you stop drinking, and then wait a little while, the alcohol will be broken down by your liver and there will no longer be alcohol in your milk.

There’s a great resource called the “TIME TO ZERO” calculator to help you know how long to wait before feeding your baby after drinking alcohol. You don’t have to pump and throw the milk out. The alcohol will be filtered out of the milk once it has left your bloodstream. While the “pump and dump” method is a myth, there are some other important things to know about using alcohol while you’re breastfeeding.

1. Alcohol inhibits the release of oxytocin. Oxytocin is a natural hormone that helps with milk let-down. The “let-down” is when the milk is released from the alveoli where it’s made and travels to the nipple for feeding. So, when someone is drinking alcohol, they’ll be less likely to give an adequate feeding when that let-down isn’t happening.
2. Consider pumping right before you drink. That way you can stay comfortable if you have to go longer than usual before pumping or feeding your baby again. Plus, you get to keep that milk and you might even want to use it later to feed your baby while alcohol leaves your body.
3. If your breasts get engorged while waiting for the alcohol levels to drop, go ahead and pump or use hand expression to remove some milk. Engorgement can lead to other problems, so it’s best to relieve it when you can. DO NOT give this milk to the baby though.
4. Alcohol is a diuretic and can cause dehydration. This can decrease milk volume. Make sure to increase your water intake when you’re drinking alcohol.
5. Drinking alcohol with food can reduce alcohol absorption which can lower your blood alcohol concentration (BAC) and get you back to a safe zone for milk more quickly.
6. As a general rule, if you’re not feeling impaired anymore, your milk is probably safe, but use the Time to Zero calculator if you feel unsure.
7. The definition of “chronic heavy drinking” is more than two drinks per day. The data shows negative effects on babies raised by a chronic heavy drinker including hormonal imbalances, sedation, and lower academic success. Some of this might be due to alcohol in the breast milk, but it could also be due to other factors that might go along with heavy drinking including social factors, stress, and childcare differences.

A lot of people choose to stay substance-free during pregnancy and while breastfeeding, but sometimes that’s impossible. In other cases, there may be MORE benefits to you taking a helpful medication.

It’s good to know there are resources available out there to help you decide, and that most medications are safe to use while breastfeeding.

Resources:
The InfantRisk Center – Call with questions about medication safety and breastfeeding: 1(806)352-2519

Interview with Dr Hale, author of Medications and Mothers’ Milk

Drugs and Lactation Database (LactMed®)

Safe alcohol use with breastfeeding including “Time to Zero” calculator

Drug entry into Human Milk- Infant Risk Center