Methylnaltrexone Injection

Name: Methylnaltrexone Injection Drug Interactions
Creator: Dr. Brian Staiger, PharmD, BCPS

4 interactions 29 cited references

Also sold as: Relistor Relistor®

About Methylnaltrexone Injection

Methylnaltrexone injection is used to treat constipation caused by opioid (narcotic) pain medications in people with chronic (on-going) pain that is not caused by cancer but may be related to a previous cancer or cancer treatment. It is also used to treat constipation caused by opioid pain medications in people with an… Read the full Methylnaltrexone Injection drug information page →

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated Aug 9, 2026 · Editorial policy · Data sources

Sources: FDA prescribing information (Structured Product Labeling), the published literature cited in each entry, DDInter 2.0 (a major open-access drug-interaction database), and legacy DrugBank interaction data distributed by the NIH's RxNav service (decommissioned in 2024) — analyzed and reviewed by our pharmacist team. How we build this library →

Most serious with: Morphine Morphine Sulfate Liposome Naldemedine Naloxegol

4 Major

All (4) Major (4)

Major

Methylnaltrexone Injection Morphine Decreased opioid efficacy and precipitation of opioid withdrawal Details Methylnaltrexone Injection Morphine Sulfate Liposome Decreased opioid efficacy and precipitation of opioid withdrawal Details Methylnaltrexone Injection Naldemedine Symproic Increased risk of opioid withdrawal Details Methylnaltrexone Injection Naloxegol Movantik Risk of opioid withdrawal Details

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Educational information only, not medical advice. Always confirm interactions with your pharmacist or prescriber before making any change to your medications.