Drug Interaction Report

Irinotecan Injection and Erythromycin: Interaction Details

A pharmacist-reviewed analysis of the Irinotecan Injection and Erythromycin 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

Erythromycin

Erythrocin Stearate
+

Irinotecan Injection

Camptosar Camptosar® Onivyde
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 96 documented Irinotecan Injection interactions, 73 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 CYP3A4 substrate exposure and an increased risk of CYP3A4-substrate-related adverse effects

Interaction Deep Dive

Concomitant use of erythromycin and CYP3A4 substrates may increase CYP3A4 substrates exposure that may increase or prolong both the therapeutic and adverse effects. Consider dosage adjustments, and when possible, closely monitor drug concentrations of CYP3A4 substrates in patients concurrently receiving erythromycin123.

Why it happens (mechanism)

Inhibition of CYP3A4-mediated metabolism by erythromycin

Common questions

Can I take Irinotecan Injection and Erythromycin together?

Increased CYP3A4 substrate exposure and an increased risk of CYP3A4-substrate-related adverse effects Always confirm with your pharmacist or prescriber before making any change.

How serious is the Irinotecan Injection and Erythromycin 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.

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Questions for your pharmacist

  • Does my dose of Irinotecan Injection or Erythromycin 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 (3)

  1. Product Information: Erythromycin Lactobionate IV injection lyophilized powder for solution, erythromycin lactobionate IV injection lyophilized powder for solution. Nexus Pharmaceuticals (per DailyMed), Lincolnshire, IL, 2024.
  2. Product Information: Erythromycin oral delayed-release capsules, erythromycin oral delayed-release capsules. Dr. Reddy's Laboratories Inc. (per DailyMed), Princeton, NJ, 2025. DailyMed
  3. Product Information: ERYTHROMYCIN ETHYLSUCCINATE oral suspension granule, erythromycin ethylsuccinate oral suspension granule. ANI Pharmaceuticals, Inc (per DailyMed), Baudette, MN, 2025. DailyMed
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Erythromycin

Keep reading about Erythromycin

All Erythromycin interactions (186)
Also serious with: Dihydroergotamine Injection Colchicine Ketoconazole Topical Lovastatin
Irinotecan Injection

Keep reading about Irinotecan Injection

All Irinotecan Injection interactions (96) Irinotecan Injection drug information
Also serious with: Rubella Virus Vaccine, Live Smallpox Monkeypox Vaccine Typhoid Vaccine Varicella Virus Vaccine, Live
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:

Erythromycin + Activated Charcoal American Hellebore Arsenic Beer Cesium Ephedra Grapefruit Oleander + 196 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.