Breastfeeding mothers may have a number of reasons they are considering taking medication. They may have pain resulting from birth, postpartum depression, or of course be dealing with health conditions completely unrelated to their pregnancies or labors.

In all of these cases, women who have just given birth may find it difficult to treat these issues because their medications are considered unsafe for breastfeeding infants. It can also be really difficult to figure out which medications are safe, and which should be avoided. So, let's dive into the science behind it.

What medications are safe to take while breastfeeding?

The American Academy of Pediatrics (AAP) opened its 2013 statement on The Transfer of Drugs and Therapeutics into Human Milk with an explanation for why physicians might tell lactating women not to breastfeed while on certain medications.

First, there may just not be any evidence—positive or negative—about the effects of a particular drug on human milk. It is often difficult to run ethical studies if there is any concern about the potential harm of a drug to an infant. Interestingly, the drug studies that physicians do base their breastfeeding recommendations on often come from animal studies, which only imperfectly apply to humans.

The AAP asserts that physicians should consider a host of factors when prescribing medications to lactating women, which include: “the need for the drug by the mother, the potential effects of the drug on milk production, the amount of the drug excreted into human milk, the extent of oral absorption by the breastfeeding infant, and potential adverse effects on the breastfeeding infant."

Given all of the factors to consider when prescribing a medication, it's no wonder there can be disagreement on whether any particular medication is safe, or why a woman's provider advises her to stop or continue breastfeeding.

When looking for drug information, new mothers might question whether a drug is safe or unsafe for breastfeeding—unfortunately answers are often not cut and dry. Given the vast array of medications available and each individual provider's experience, the “safe or unsafe" question might be answered differently by different people.

When making the choice to take a medication and pause or discontinue breastfeeding, nursing mothers might do well to think less in terms of absolutes and more in terms of concentration, in collaboration with their provider, of course.

Consider the concentration of a drug

The first way to think about medication and breastfeeding is in terms of dosage. Consider a drug many people don't even think of as a drug: Caffeine. Drink 0.1 grams (the amount of caffeine in one cup of coffee), and you'll find it easier to make it through your day after three middle-of-the-night wake-ups. Ingest 30 grams, as two students recently did when they were accidentally overdosed during a research study, and if you're lucky, you'll end up in intensive care.

In the case of nursing mothers, dosing is especially complicated. The prescribing physician has to consider not just the right dose for the mother, but also a safe dose for the child who may receive some of that drug through the mother's breast milk.

To make calculations about how much of any particular drug will be present in breast milk, the physician must consider how that drug travels to different parts of the body. In pharmacology, this is called distribution. Some medications are water-soluble, meaning that they dissolve in water, while other medications are fat-soluble.

The solubility of a drug determines how that drug will be distributed throughout the body. Alcohol, for example, is water-soluble. Furthermore, it dissolves quickly in water, which is why it moves so rapidly from the intestines to the bloodstream, and from the bloodstream throughout the body. Alcohol's solubility is part of the reason it is found only in trace amounts in breast milk and generally regarded as safe to drink while breastfeeding.

Is over the counter pain medication safe while breastfeeding?

Many classes of pain medications are also water-soluble. Women who have had C-sections are often given morphine, also a water-soluble drug, because it appears only in trace amounts in breast milk.

The commonly used acetaminophen and ibuprofen are generally considered safe.

Medications are said to be “lipophilic" when they have a tendency to concentrate in fat. Because breast milk contains a high proportion of fat, it will also contain a high proportion of a drug that dissolves in fat. Therefore, fat-soluble medications are often prescribed with caution.

Is anxiety medication safe while breastfeeding?

SSRIs, which are prescribed for anxiety and depression, are lipophilic and have relatively long half-lives, meaning that they both dissolve in fat and take longer to metabolize. Although the infant exposure to SSRIs through breast milk is still relatively low, there have not been long-term studies of this exposure, so women who need these drugs may be discouraged from breastfeeding.

The solubility of a medication is just one of a host of factors physicians need to consider when making a recommendation about breastfeeding while on that medication. New drugs are introduced all the time, and drugs that were previously thought to be safe for mothers to take while breastfeeding are sometimes found to be unsafe (codeine is one such example).

LactMed, a database maintained by the U.S. National Library of Medicine, is regularly updated with new drug information and can be used to help evaluate whether a particular medication is safe for a nursing infant.

Concentration of the parent

The concentration of a particular drug is important because of the amounts that may appear in breast milk. If that amount is deemed too high, a woman might be counseled to stop breastfeeding, or at least to change the dosage of the drug. According to the American Academy of Pediatrics, remarkably few medications absolutely require breastfeeding cessation.

But the concentration of a drug in the mother's milk is only one way to think about concentration. It's also important for prescribing physicians to consider “concentration" as a mental state. Narcotics like morphine can interfere with awareness, so even if they won't pass into the bloodstream, they may temporarily incapacitate the mother.

While that mother's milk may be completely safe for the infant, that mother's diminished concentration may make it less safe for her to be holding—and therefore nursing—the baby.

A more conservative approach might be to feed a baby expressed milk or formula until the medication wears off.

In other cases, physicians might be weighing the mother's ability to safely care for her baby against her ability to nurse that baby. This is often the consideration when prescribing antidepressants which may require cessation of breastfeeding.

Concentration of the provider

In weighing potentially competing recommendations about whether or not to stop nursing while on medication, it's also worth focusing on the physician's concentration. The safety of the infant is obviously of concern to any provider prescribing a medication to a nursing mother. But it's important to note that, in cases where medication is deemed medically necessary for a lactating mother, the mother—not the baby—is the patient.

Although women should feel comfortable asking questions about alternative medications that may make it easier to continue breastfeeding, it's worth noting that at a time when everything now appears to revolve around the baby, the mother's provider will focus on the mother. Because of this, a physician may make recommendations about the mother's health that may be momentarily at odds with her plans to breastfeed.

So, can I take medication while breastfeeding?

When weighing the decision to take a medication and pause or stop breastfeeding, nursing mothers should consider all three of the above forms of concentration. They can ask their providers about the dosage and its possible effects on breast milk. They can ask how a medication deemed safe for breastfeeding might impact their own mental state. And they can ask for advice in weighing the health impacts of the medication against the drawbacks of pausing or stopping breastfeeding.

There are rare times when the best decision may be to pause breastfeeding or stop breastfeeding altogether. At those times, it's important to consider one last form of concentration. Infant formula is also a “concentration," a combination of proteins, fats, and carbohydrates.

The decision to use formula while on a potent medication can feel like a failure to many mothers, who are flooded with messages about the importance of breastfeeding. But if short-term formula use can ensure a long-term benefit for the mother, that mother can be a healthy parent to her baby for life.

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