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Naltrexone - Vivitrol and breastfeeding

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  • #1

    Naltrexone - Vivitrol and breastfeeding

    I am hoping to get some information about these medications in breastfeeding.

    I am an anesthesiologist currently in recovery. I got addicted to opiates following a miscarriage. I got pregnant several months after the miscarriage and was fortunate enough to get the help I needed right after finding out about the pregnancy. In order to return back to the OR, the state monitoring board wants me to take vivitrol.

    I am two months post-partum and will need to return to work after 3 months (i.e. in a month). I would ideally like to continue breastfeeding however, the studies on naltrexone are concerning. Lactamed states naltrexone/vivitrol is safe in breastfeeding but, the drug manufacturer states it is not safe. There is only one study conducted on naltrexone and breastfeeding that I could find. It was low dose naltrexone and a metabolite of the mediation was found in the breast milk.

    I would love to get more information, if there is any and some advice.

    I greatly appreciate any advice/help.
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  • #2
    Dear loveumms,

    Naltrexone (Vivitrol) is considered L1 (safest category). L5 medications are considered contraindicated during lactation. The relative infant dose (the amount of your dose that enters breastmilk) is 1.4 percent. For most medications, a relative infant dose less than ten percent is considered compatible with breastfeeding. The time the medication is highest in your breastmilk is one hour after your dose so try to avoid breastfeeding at that time. The half-life is 4 to 13 hours. The oral bioavailability is 96 percent. Dr. Hale's clinical recommendation is as follows: [Naltrexone is a long acting narcotic antagonist similar in structure to naloxone. In a study of one patient receiving 50 mg/day, the average concentration of naltrexone and 6-beta-naltrexol (metabolite) in milk were 1.7 and 46 µg/L. The milk/plasma ratios of naltrexone and 6-beta-naltrexol were 1.9 and 3.4 respectively. The absolute infant dose was 0.26 and 6.86 µg/kg/day, respectively. The authors suggest the relative infant dose is 0.06 and 1.0% (range = 0.86-1.06%). The infant was reported to have achieved all expected milestones and showed no drug-related side effects. Naltrexone was undetectable in the infants' plasma and levels of 6-beta-naltrexol were only marginally detectable, at 1.1 µg/L.] This level is unlikely to cause clinical side effects in the breastfed infant. If you have further questions, please call the InfantRisk Center at 806-352-2519. We are open Monday through Friday, 8 to 5, CST.

    Sincerely,
    Cindy Pride, MSN, CPNP
    TTUHSC InfantRisk Center

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    • #3
      Thank you for the information.

      Is there any information about the long acting injection formulation (vivitrol)?

      Additionally, if this has not been studied, how would one go about testing breast milk for medication metabolites? If it has not been studied, I would really like to have it tested to determine if the milk quantities are similar to oral dosing (and safe for breastfeeding).

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      • #4
        Loveumms:

        No, there are no data on vivitrol as of yet. I would suspect the levels in milk will not be much different from above.

        Without a funded clinical trial, there is no way to get it studied in breastmilk. Sorry.

        Tom Hale Ph.D.

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        • #5
          Dr. Hale,

          I was doing further research on this issue and wanted to confirm that the study you are speaking of the mother was indeed taking 50mg per day of naltrexone. The only study I could find, the mother was taking 5mg/day. This is a 10 times higher dose and would be perceived to give the infant a 10 times amount, is that correct.

          If I am interpreting this study correctly, the infant will receive 1% of the total dose of what the mother takes. If the mother is taking 50mg that would be .5mg per day the infant would receive, or am I incorrect in my assumptions.

          If the half life is 6-13 hours, this would mean that half the dose would still be present at 12 hours after dose. Therefore, if you are taking 50mg, that means you would still have approximately 25mg in the plasma blood - if 1% is being given to the infant this would still be .25mg which I would assume would be a decent dose in a 8kg infant. Please let me know if I am interpreting this wrong.

          THANK YOU!
          Last edited by loveumms; 01-01-2013, 08:48 PM.

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          • #6
            Here is the link to the study I was using:
            http://www.ncbi.nlm.nih.gov/pubmed/15296587

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