Drug Interaction Report

Doxorubicin and Valspodar: Interaction Details

A pharmacist-reviewed analysis of the Doxorubicin and Valspodar 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

Doxorubicin

Adriamycin Adriamycin® Caelyx Doxil Rubex®
+

Valspodar

No brand names on record
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 237 documented Doxorubicin interactions, 218 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
rapid
Evidence
probable
Severity
Major

What happens

An increased risk of DOXOrubicin toxicity

Interaction Deep Dive

A significant decrease in the clearance of DOXOrubicin and doxorubicinol has been observed during combined administration with valspodar23. This resulted in enhanced DOXOrubicin toxicity. DOXOrubicin dose reductions of up to 75% were required in multiple myeloma patients receiving VAD (vincristine, DOXOrubicin, dexamethasone) in one study 2. Further studies to define guidelines for DOXOrubicin dose reduction are needed. Although no formal drug interaction studies have been done with DOXOrubicin hydrochloride liposome injection, it may interact with drugs known to interact with the conventional formulation of DOXOrubicin 1.

Why it happens (mechanism)

Inhibition of p-glycoprotein-mediated biliary transport of DOXOrubicin by valspodar

Common questions

Can I take Doxorubicin and Valspodar together?

An increased risk of DOXOrubicin toxicity Always confirm with your pharmacist or prescriber before making any change.

How serious is the Doxorubicin and Valspodar interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.

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 Doxorubicin or Valspodar 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: DOXIL(R) intravenous injection, doxorubicin HCl liposome intravenous injection. Janssen Products, LP (per FDA), Horsham, PA, 2012. DailyMed
  2. Sonneveld P, Marie JP, Huisman C, et al: Reversal of multidrug resistance by SDZ PSC833, combined with VAD (vincristine, doxorubicin, dexamethasone) in refractory multiple myeloma. A phase I study. Leukemia 1996; 10:1741-1750.
  3. Fischer V, Rodriguez-Gascon A, Heitz F, et al: The multidrug resistance modulator valspodar (PSC833) is metabolized by human cytochrome#P450#3A. Implications for drug-drug interactions and pharmacological activity of the main metabolite. Drug Metab Disp 1998; 26:802-811.
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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:

Doxorubicin + Grapefruit St. John's Wort Acacia Rigidula Acerola Adrafinil African Wild Potato Alpha-lipoic Acid American Elder + 131 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.