Drug Interaction Report

Morphine Injection and Butorphanol: Interaction Details

Name: Morphine Injection and Butorphanol Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Morphine Injection and Butorphanol interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Butorphanol

Butorphic Dolorex Solution Torbugesic Torphadine Vetorphic

Morphine Injection

Astramorph® PF Duramorph Duramorph® Infumorph Infumorph® Kadian Mitigo MS Contin

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Major

Potentially serious — often needs a change or close monitoring.

Minor

Moderate

Major

Contraindicated

How we grade severity & evidence

Severity levels

Contraindicated: These should generally not be used together.
Major: Potentially serious — often needs a change or close monitoring.
Moderate: Can be significant — usually manageable with monitoring.
Minor: Usually limited clinical impact.

Evidence grades

Established: Well documented — supported by controlled studies or strong clinical data.
Probable: Good supporting evidence, though not definitively proven.
Suspected: Some evidence suggests this interaction, but it is not well established.
Possible: Limited or conflicting evidence; the interaction may occur.
Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 437 documented Morphine Injection interactions, 409 are rated major — including this one.

Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.

Onset

unspecified

Evidence

theoretical

Severity

Major

What happens

Reduced analgesic effect or precipitation of withdrawal symptoms, and an increased risk of serotonin syndrome

Interaction Deep Dive

Avoid concomitant use of morphine with a mixed opioid agonist/antagonist or a partial agonist opioid analgesic as this may reduce the analgesic effect of morphine and may precipitate withdrawal symptoms. Additionally, observe the patient carefully when using morphine concomitantly with other drugs that affect the serotonergic system, especially during initiation and titration, as risk for serotonin syndrome is increased; discontinue if suspected⁷⁵¹⁴³²⁶.

Why it happens (mechanism)

Opioid receptor antagonism; additive serotonergic effects

Literature reports

1 report — tap to read

a) Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs ⁵¹⁴.

Common questions

Can I take Morphine Injection and Butorphanol together?

Reduced analgesic effect or precipitation of withdrawal symptoms, and an increased risk of serotonin syndrome Always confirm with your pharmacist or prescriber before making any change.

How serious is the Morphine Injection and Butorphanol interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

Does my dose of Morphine Injection or Butorphanol need adjusting while I take them together?
What symptoms should prompt me to call you or my prescriber right away?
Does the timing of my doses matter for this combination?
Is there a safer alternative to one of these medications for me?

References (7)

Product Information: MS CONTIN(R) oral extended-release tablets, morphine sulfate oral extended-release tablets. Purdue Pharma LP (per FDA), Stamford, CT, 2023. DailyMed
Product Information: INFUMORPH intrathecal, epidural injection, morphine sulfate intrathecal, epidural injection. Hikma Pharmaceuticals USA Inc (per FDA), Berkeley Heights, NJ, 2023. DailyMed
Product Information: Morphine sulfate oral tablets, morphine sulfate oral tablets. Hikma Pharmaceuticals USA Inc.(Per FDA), Berkeley, NJ, 2023. DailyMed
Product Information: Morphine sulfate oral solution, morphine sulfate oral solution. Hikma Pharmaceuticals USA Inc (per FDA), Berkeley Heights, NJ, 2023. DailyMed
Product Information: DURAMORPH intravenous, epidural, intrathecal injection, morphine sulfate intravenous, epidural, intrathecal injection. Hikma Pharmaceuticals USA Inc (Per FDA), Berkeley, NJ, 2023. DailyMed
Product Information: Morphine sulfate intravenous injection, morphine sulfate intravenous injection. Mallinckrodt Inc (Per FDA), St. Louis, MO, 2023. DailyMed
Product Information: ARYMO(TM) ER oral extended-release tablets, morphine sulfate oral extended-release tablets. Egalet US Inc (per manufacturer), Wayne, PA, 2017. DailyMed

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Butorphanol

Keep reading about Butorphanol

All Butorphanol interactions (35)

Also serious with: Acetaminophen And Codeine Palonosetron Injection Linezolid Injection Diphenhydramine Injection

Morphine Injection

Keep reading about Morphine Injection

All Morphine Injection interactions (437) Morphine Injection drug information

Also serious with: Rasagiline Procarbazine Phenelzine Ozanimod

Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Butorphanol + 1,4-butanediol Activated Charcoal Beer Gamma-hydroxybutyrate (ghb) Kava L-tryptophan Wine 5-htp + 92 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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A message from HelloPharmacist

About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.