Acetaminophen and codeine and Methylnaltrexone interaction
Acetaminophen and codeine and Methylnaltrexone: both prescribing labels 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 Methylnaltrexone (Relistor) label · effective 2024-05-01
• Other Opioid Antagonists : Potential for additive effect and increased risk of opioid withdrawal; avoid concomitant use.
Other Opioid Antagonists Avoid concomitant use of RELISTOR with other opioid antagonists because of the potential for additive effects of opioid receptor antagonism and increased risk of opioid withdrawal.
• Opioid Withdrawal : Consider the overall risk benefit in patients with disruptions to the blood-brain barrier.
Monitor closely for symptoms of opioid withdrawal.
Patients having disruptions to the blood-brain barrier may be at increased risk for opioid withdrawal and/or reduced analgesia.
From the Acetaminophen and codeine (ACETAMINOPHEN AND CODEINE PHOSPHATE) label · effective 2026-01-22
Consider recommending or prescribing an opioid overdose reversal agent ( see WARNINGS, Life-Threatening Respiratory Depression ; DOSAGE AND ADMINISTRATION, Patient Access to Naloxone for the Emergency Treatment of Opioid Overdose ).
If concomitant use is warranted, consider recommending or prescribing an opioid overdose reversal agent ( see WARNINGS, Life-Threatening Respiratory Depression ; DOSAGE AND ADMINISTRATION , Patient Access to Naloxone for the Emergency Treatment of Opioid Overdose ).
Patient Access to an Opioid Overdose Reversal Agent for the Emergency Treatment of Opioid Overdose Inform patients and caregivers about opioid overdose reversal agents (e.g., naloxone, nalmefene).
Explain to patients and caregivers that effects of opioid overdose reversal agents like naloxone and nalmefene are temporary, and that they must call 911 or get emergency medical help right away in all cases of known or suspected opioid overdose, even if an opioid overdose reversal agent is administered ( see OVERDOSAGE ) .
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.