Drug Interaction Report

Granisetron Transdermal Patch and Telithromycin: Interaction Details

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

Telithromycin

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
theoretical
Severity
Major

What happens

Increased granisetron plasma concentrations and an increased risk of QT interval prolongation

Interaction Deep Dive

The concomitant use of granisetron with ketoconazole (a strong CYP3A4 inhibitor) resulted in inhibition of granisetron metabolism. Although the interaction with granisetron and telithromycin has not been evaluated, caution should be used when granisetron (a QT-prolonging drug)1 is coadministered with a strong CYP3A4 inhibitor that also prolongs the QT interval, such as telithromycin, due to the potential for increased granisetron exposure and risk of additive QT prolongation and serious ventricular arrhythmias. If coadministration is required, granisetron dose adjustment may be warranted 2. Closely monitor ECG for QT interval prolongation during concomitant therapy.

Why it happens (mechanism)

Additive effects on QT interval prolongation; inhibition of CYP3A4-mediated granisetron metabolism by telithromycin

Common questions

Can I take Granisetron Transdermal Patch and Telithromycin together?

Increased granisetron plasma concentrations 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 Telithromycin 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 Granisetron Transdermal Patch or Telithromycin 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)

  1. Product Information: KYTRIL(R) IV injection, granisetron HCl IV injection. Genentech USA, Inc, South San Francisco, CA, 2011.
  2. Product Information: KETEK(R) oral tablets, telithromycin oral tablets. Sanofi-Aventis, US, LLC, Bridgewater, NJ, 2010. DailyMed
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Telithromycin

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All Telithromycin interactions (146)
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Granisetron Transdermal Patch

Keep reading about Granisetron Transdermal Patch

All Granisetron Transdermal Patch interactions (281) Granisetron Transdermal Patch drug information
Also serious with: Phenelzine Pimozide Piperaquine Saquinavir
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:

Telithromycin + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Sida Cordifolia St. John's Wort + 170 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.