Naltrexone While Breastfeeding: What LactMed and the Research Say

LactMed, the NIH's authoritative drug-in-lactation database, lists naltrexone as compatible with breastfeeding and supported by direct measurements of very low infant exposure. Here is what that actually means for a new parent.

What You'll Learn:

• What LactMed is and why its rating for naltrexone matters.

• The actual numbers on how much naltrexone passes into breast milk.

• What the one published infant exposure study found.

• How to think about timing doses and when to consult a pediatrician.

• Why postpartum is a particularly common time to start or restart naltrexone.

Breastfeeding adds a layer of worry to nearly every medication decision a new parent faces. For anyone managing alcohol cravings or alcohol use disorder in the postpartum period, naltrexone is usually one of the first questions that comes up. The good news is that the data on this one is relatively clear, and it is reassuring.

This article is educational. It is not medical advice, and no article can replace a conversation with your own prescribing clinician and your baby's pediatrician. But it will give you a concrete picture of what the evidence shows so that conversation can be a productive one.

LactMed and Why Its Naltrexone Rating Matters

LactMed is a free, peer-reviewed database maintained by the U.S. National Library of Medicine that summarizes what is known about drugs and breastfeeding. Clinicians, pharmacists, and lactation consultants treat it as a reference standard. It is updated regularly as new research comes in, and it distinguishes between drugs with strong safety data, drugs where caution is warranted, and drugs where breastfeeding should be interrupted.

LactMed's current entry on oral naltrexone is straightforward. Limited data indicate that naltrexone is minimally excreted into breast milk, and if the mother requires naltrexone, it is not a reason to discontinue breastfeeding. That language matters. The database does not say "probably okay" or "use with caution." It says naltrexone use is not a reason to stop breastfeeding.

This is consistent with broader professional guidance. The Academy of Breastfeeding Medicine considers medications used in the treatment of substance use disorders, including oral naltrexone, to be compatible with lactation when prescribed appropriately.

How Much Naltrexone Actually Reaches a Breastfed Infant

This is where the evidence gets specific. According to the direct measurements summarized by LactMed, an exclusively breastfed infant whose parent is taking a standard 50 mg daily dose of oral naltrexone would receive about 7 micrograms per kilogram of body weight per day from milk, including the active metabolite beta-naltrexol.

To put that in perspective, that intake is equivalent to roughly 0.86 percent of the parent's weight-adjusted dose. Lactation pharmacology generally regards an infant dose under 10 percent of the parent's weight-adjusted dose as low enough that clinically meaningful effects are unlikely. Naltrexone falls well under that threshold.

The one published study that measured the actual infant, rather than just the milk, looked at a 1.5-month-old breastfed baby whose parent was taking 50 mg of oral naltrexone daily. Both naltrexone and beta-naltrexol were undetectable in the infant's blood 9.5 hours after the parental dose. The infant had no adverse effects and met expected developmental milestones throughout the observation period.

A single case report is not definitive. But combined with the milk-level measurements and the drug's pharmacology, the picture is internally consistent. The amount of naltrexone a breastfed infant is exposed to is very small, and the infant's body does not appear to accumulate it.

Why the Postpartum Period Is a Common Time to Restart

Many people who wanted to use naltrexone during pregnancy chose to wait, either because their clinician preferred to avoid non-essential medication or because they felt more comfortable postponing the decision. As we discuss in our guide to naltrexone during pregnancy, that decision is more nuanced than it used to be, but many patients still decide to delay.

Postpartum often brings the question back for a specific reason. Alcohol cravings that had been manageable can return or intensify, and risk of relapse tends to climb in the months after delivery. Sleep deprivation, mood changes, identity shifts, and the absence of the structure that pregnancy imposed all contribute. For someone who knows drinking is creeping back in, the breastfeeding question becomes practical and time-sensitive.

This is a reasonable time to have the conversation with a clinician. As we note in our article on women and alcohol, women face physiological and social pressures around drinking that do not pause for the postpartum period. Addressing cravings early, rather than waiting until drinking has fully re-established itself, is usually easier on everyone.

Timing, Dosing, and Practical Logistics

For most standard 50 mg daily dosing, the evidence does not suggest a need to pump and dump or to time feedings around doses. Infant exposure is low regardless. That said, some parents prefer to take their dose immediately after the longest feeding stretch, typically at night, so that several hours pass before the next feed. This is more of a personal preference than a clinical requirement.

A few practical points worth knowing:

• Naltrexone's half-life in adults is about 4 hours, and its active metabolite beta-naltrexol has a half-life of roughly 13 hours. Milk levels of the parent compound drop quickly.

• No dose adjustment is typically needed because of breastfeeding. The 50 mg daily dose used for alcohol cravings is the same dose studied in the infant-exposure literature.

• Regular naltrexone does not affect milk supply in the direct, hormonal way some medications do. There is no mechanistic reason to expect supply problems, and none have been reported in the available case literature.

For anyone starting naltrexone for the first time, our article on how long you need to take naltrexone covers expectations around duration of use in general, which applies to postpartum patients too.

When to Involve the Pediatrician

A good default is to mention naltrexone at the next well-baby visit, or sooner if starting the medication is new. You do not need to ask permission, but the pediatrician will want it in the chart and can help you watch for anything unexpected.

What would unexpected look like? Based on the available data, sedation, poor feeding, or unusual irritability would be worth flagging. None of these have been reported in the published cases, but it is always reasonable to have a second clinician watching for them.

For a broader overview of how medications pass into breast milk, the American Academy of Pediatrics policy statement is a useful reference. It is written for clinicians but is readable and covers the general principles that apply to most oral medications.

What About Alcohol and Breast Milk Separately

This article is about naltrexone, not about drinking. But the two questions often show up together, so it is worth naming the distinction. Alcohol itself passes freely into breast milk and peaks at a concentration close to what is in the parent's bloodstream, typically 30 to 60 minutes after a drink. The Centers for Disease Control and Prevention has clear guidance on timing feedings around drinking for parents who choose to drink occasionally. But for someone whose goal is to reduce or stop drinking rather than to time it, naltrexone is specifically designed to address the cravings that make reduction hard in the first place.

The practical point is this. Using naltrexone to reduce drinking while breastfeeding is a very different situation than drinking while breastfeeding. The medication exposure is small and appears safe. The alcohol exposure is not small, and reducing it is good for both parent and infant.

A Note on Emergency Situations

If you are taking a prescription opioid medication for pain, or any opioid medication at all, do not start naltrexone without telling your prescribing clinician first. Naltrexone blocks opioid receptors and can precipitate severe withdrawal in someone with opioids in their system. This is true regardless of breastfeeding status. It is one of the standard screening questions before starting the medication, and it matters.

If you experience severe alcohol withdrawal symptoms like tremors, rapid heartbeat, confusion, or seizures when you try to stop drinking, seek emergency care. Withdrawal can be medically serious and should not be managed at home. Breastfeeding does not change that recommendation.

Bottom Line

Naltrexone and breastfeeding is one of the more clearly answered medication questions in alcohol care. The LactMed data shows minimal transfer into breast milk, the one available infant exposure study showed no detectable drug and no adverse effects, and authoritative professional bodies consider the medication compatible with lactation. None of that means the decision is automatic, but it does mean it is reasonable and well-supported.

If alcohol cravings are creeping back into your postpartum life and you are wondering what to do, our online Alcohol Use Assessment can give you a clearer picture of where you stand and whether naltrexone might fit. Our clinical team works with postpartum patients regularly and can help you navigate the decision alongside your pediatrician and obstetric clinician.

This article is educational and is not medical advice. Decisions about starting, continuing, or stopping any prescription medication during breastfeeding should be made with a qualified clinician who knows your full medical history and your baby's.