Naloxone and Naltrexone interaction
Naloxone and Naltrexone: the Naltrexone prescribing label flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Naltrexone label · effective 2026-01-30
Any individual who has failed the naloxone challenge test or has a positive urine screen for opioids [see Warnings and Precautions ( 5.3 ) ] .
Any individual who has failed the naloxone challenge test or has a positive urine screen for opioids (4) .
Strongly consider recommending or prescribing an opioid reversal agent (e.g., naloxone, nalmefene) for the emergency treatment of opioid overdose (5.1) .
…Overdose Reversal Agent for the Emergency Treatment of Opioid Overdose At the initial naltrexone for extended-release injectable suspension injection and with each subsequent injection, inform patients and caregivers about opioid overdose reversal agents (e.g., naloxone, nalmefene) and discuss the importance of having access to an opioid overdose reversal agent.
A naloxone challenge test may be helpful; however, a few case reports have indicated that patients may experience precipitated withdrawal despite having a negative urine toxicology screen or tolerating a naloxone challenge test (usually in the setting of transitioning from buprenorphine treatment).
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.