Drug Interaction Report

Granisetron Transdermal Patch and Venlafaxine: Interaction Details

A pharmacist-reviewed analysis of the Granisetron Transdermal Patch and Venlafaxine 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

Venlafaxine

No brand names on record
+

Granisetron Transdermal Patch

Sancuso Sancuso®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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 281 documented Granisetron Transdermal Patch interactions, 265 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
probable
Severity
Major

What happens

An increased risk of serotonin syndrome and an increased risk of QT interval prolongation

Interaction Deep Dive

Concomitant use of venlafaxine and other QT interval prolonging serotonergic drugs may increase the risk of serotonin syndrome and additional QT interval prolongation. Signs and symptoms may include mental status changes (eg, agitation, hallucinations, delirium, and coma), autonomic instability (eg, tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (eg, tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, and gastrointestinal symptoms such as nausea, vomiting or diarrhea. If concomitant use is required, notify patients of the increased risk of serotonin syndrome and monitor for symptoms. Immediately discontinue treatment with venlafaxine and any concomitant serotonergic agent if symptoms occur and initiate supportive treatment1.

Why it happens (mechanism)

Additive serotonergic effects; additive QT interval prolongation

Common questions

Can I take Granisetron Transdermal Patch and Venlafaxine together?

An increased risk of serotonin syndrome and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.

How serious is the Granisetron Transdermal Patch and Venlafaxine 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Granisetron Transdermal Patch or Venlafaxine 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 (1)

  1. Product Information: EFFEXOR XR(R) oral extended-release capsules, venlafaxine oral extended-release capsules. Viatris Specialty (per FDA), Morgantown, WV, 2023. DailyMed
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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:

Venlafaxine + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Lithium Sida Cordifolia + 102 more

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

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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.