Morphine Injection and Yohimbine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Morphine Injection
Yohimbine
No brand names on record
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.
What happens
Increased analgesic and adverse effects of morphine
Interaction Deep Dive
Pretreatment with yohimbine prior to dental surgery enhanced the analgesic effect of morphine in patients1. Yohimbine selectively antagonizes alpha2-receptors, which alters norepinephrine release. Yohimbine administered sub-chronically may produce changes in alpha-receptor number or sensitivity, act on a specific, yet unknown alpha2-receptor subtype, or act peripherally to antagonize the effect of norepinephrine, thereby altering the pain response 1. It is unclear if adverse effects of morphine such as respiratory depression may be similarly increased. Patients taking yohimbine and morphine concomitantly should be monitored closely for analgesic and adverse effects.
Why it happens (mechanism)
Alteration of pain response by yohimbine
Literature reports
1 report — tap to read
a) Yohimbine administered orally prior to dental surgery significantly enhanced the analgesic effect of morphine (p equal to 0.038) in 30 male patients in a randomized, double-blind, placebo-controlled study. Yohimbine 5.4 milligrams or placebo was administered orally three times daily for 3 days prior to surgery, then 6 hours prior to surgery, and immediately prior to surgery. Morphine 8 mg was administered intravenously after surgery. Pain was rated by patients using a visual analog scale. Morphine analgesia appeared to decrease to baseline after about 2.5 hours in patients receiving placebo; whereas analgesia remained elevated in yohimbine-treated patients. No adverse effects were reported 1.
Common questions
Can I take Morphine Injection and Yohimbine together?
Increased analgesic and adverse effects of morphine Always confirm with your pharmacist or prescriber before making any change.
How serious is the Morphine Injection and Yohimbine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Morphine Injection or Yohimbine 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 anything you'd monitor while I'm on both?
References (1)
- Gear RW, Gordon NC, Heller PH, et al: Enhancement of morphine anangesia by the alpha2-adrenergic antagonist yohimbine. Neuroscience 1995; 66(1):5-8.
Keep reading about Morphine Injection
Keep reading about Yohimbine
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