Can you take naltrexone while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
Limited data indicate that naltrexone is minimally excreted into breastmilk. If the mother requires naltrexone, it is not a reason to discontinue breastfeeding.
Quoted from Naltrexone — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised February 15, 2026.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of naltrexone. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
How much naltrexone gets into breastmilk
Naltrexone is used as maintenance treatment of opiate dependence in opiate-detoxified patients. Peak plasma levels of 40 to 50 mcg/L at 1 hour after the dose and average plasma levels of 3 to 5 mcg/L have been reported in adults taking daily maintenance doses. Oral bioavailability is 5 to 40% in adults. Naltrexone is metabolized to active beta-naltrexol and to other inactive metabolites.
Maternal Levels. One lactating woman who was 1.5 months postpartum and taking 50 mg of oral naltrexone daily during pregnancy and lactation had her milk sampled several times between 3.7 and 23 hours after her dose. Naltrexone milk levels were undetectable (<2 mcg/L) by 8 hours after the dose while beta-naltrexol milk levels remained detectable throughout the study period and averaged 46 mcg/L. The half-life of elimination from milk was 2.5 and 7.7 hours for naltrexone and beta-naltrexol, respectively. The authors estimated that an exclusively breastfed infant would receive about 7 mcg/kg daily of naltrexone including the active metabolite, equivalent to 0.86% of the maternal weight-adjusted dosage.
In a study of the pharmacokinetics of naltrexone in pregnant women, one mother had a milk sample analyzed for naltrexone and 6-beta-naltrexol 25 days after her last injection of long-acting naltrexone XR and 31 days postpartum. The naltrexone concentration was 9.58 mcg/L and the 6-beta-naltrexol concentration was 14.7 mcg/L. The molar sum of the two values indicated that the relative infant dose was 0.83% of the maternal dose.
Infant Levels. A 1.5 month-old breastfed male infant of a mother who was taking 50 mg of oral naltrexone daily during pregnancy and lactation had undetectable (<2 mcg/L) plasma levels of both naltrexone and beta-naltrexol 9.5 hours after the maternal dose, 30 minutes after starting a feeding.
In a study of the pharmacokinetics of naltrexone in pregnant women, a 31-day-old breastfed infant had a plasma sample analyzed for naltrexone and 6-beta-naltrexol 25 days after the mother’s last injection of long-acting naltrexone XR. The naltrexone concentration was 10.3 mcg/L and the 6-beta-naltrexol concentration was 15.8 mcg/L.
What has been seen in breastfed infants
A 1.5-month-old breastfed infant of a mother who was taking 50 mg of oral naltrexone daily during pregnancy and lactation was reportedly healthy with no naltrexone-related adverse effects.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take naltrexone while breastfeeding?
Limited data indicate that naltrexone is minimally excreted into breastmilk. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
What can I take instead of naltrexone while breastfeeding?
LactMed lists Buprenorphine, Methadone as alternate drugs to consider. That is the database's own list for this drug — whether any of them suits you depends on what you are treating.
Does naltrexone pass into breastmilk?
LactMed's measured drug levels for naltrexone are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking naltrexone?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on naltrexone
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.