Phenelzine and Venlafaxine Interaction
Drug interaction information between Phenelzine and Venlafaxine.
Phenelzine and Venlafaxine have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Phenelzine and Venlafaxine. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Both medications increase serotonin levels, and using them together can cause a severe reaction. This happens because the body cannot process the excess serotonin safely.
What To Do
Do not use these drugs together. Ensure there is a proper waiting period if you are stopping one and starting the other.
FDA Label Information
Drug Interactions In patients receiving nonselective monoamine oxidase (MAO) inhibitors in combination with serotoninergic agents (e.g., dexfenfluramine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram, venlafaxine) there have been reports of serious, sometimes fatal, reactions.
Phenelzine Also Interacts With
- Sertraline moderate
- Fluoxetine moderate
- Citalopram moderate
- Fluvoxamine moderate
- Desvenlafaxine moderate
Venlafaxine Also Interacts With
- Aspirin moderate
- Metoprolol minor
- Fluoxetine minor
- Alprazolam minor
- Warfarin minor
Frequently Asked Questions
Can I take Phenelzine and Venlafaxine together?
This is a moderate interaction. Do not use these drugs together. Ensure there is a proper waiting period if you are stopping one and starting the other.
How serious is the interaction between Phenelzine and Venlafaxine?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Phenelzine and Venlafaxine interact?
Both medications increase serotonin levels, and using them together can cause a severe reaction. This happens because the body cannot process the excess serotonin safely.
Understanding the Phenelzine and Venlafaxine Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Phenelzine belongs to the Monoamine Oxidase Inhibitor (MAOI) class and Venlafaxine belongs to the Serotonin-Norepinephrine Reuptake Inhibitor (SNRI) class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Both medications increase serotonin levels, and using them together can cause a severe reaction. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Phenelzine has 27 total documented interactions on file in this dataset, and Venlafaxine has 22. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Do not use these drugs together. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Phenelzine or Venlafaxine based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.