Diphenhydramine Injection and Tranylcypromine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Tranylcypromine
Diphenhydramine Injection
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 risk of anticholinergic effects and an increased risk of CNS depression
Interaction Deep Dive
Concomitant use of tranylcypromine, an MAOI, or use in rapid succession with non-selective H1 receptor antagonists is contraindicated due to the risk of increased anticholinergic effects. If tranylcypromine is being initiated following discontinuation of a non-selective H1 receptor antagonist, allow at least 4 to 5 half-lives of the non-selective H1 receptor antagonists to elapse prior to initiating tranylcypromine. The potential for interactions after discontinuation of tranylcypromine may persist for up to 10 days until MAO activity is sufficiently recovered12. Concomitant use of tranylcypromine with CNS depressants may also increase the risk of CNS depression 2.
Why it happens (mechanism)
Additive anticholinergic effects; additive CNS depression
Common questions
Can I take Diphenhydramine Injection and Tranylcypromine together?
Increased risk of anticholinergic effects and an increased risk of CNS depression Always confirm with your pharmacist or prescriber before making any change.
How serious is the Diphenhydramine Injection and Tranylcypromine interaction?
It is rated contraindicated. These should generally not be used together.
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 Diphenhydramine Injection or Tranylcypromine 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 (2)
- Product Information: PARNATE(R) oral tablets, tranylcypromine oral tablets. Concordia Pharmaceuticals, Inc. (per FDA), Kansas City, MO, 2018. DailyMed
- Product Information: Tranylcypromine oral tablets, tranylcypromine oral tablets. Solco Healthcare US, LLC (per DailyMed), Somerset, NJ, 2024. DailyMed
Keep reading about Tranylcypromine
Keep reading about Diphenhydramine Injection
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