Drug Interaction Report

Busulfan Injection and Thioguanine: Interaction Details

A pharmacist-reviewed analysis of the Busulfan Injection and Thioguanine 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

Busulfan Injection

Busulfex Busulfex® Injection Myleran
+

Thioguanine

Tabloid Tabloid®
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
Moderate
Can be significant — usually manageable with 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 36 documented Busulfan Injection interactions, 5 are rated moderate — including this one.
Onset
delayed
Evidence
established
Severity
Moderate

What happens

An increased risk of nodular regenerative hyperplasia of the liver

Interaction Deep Dive

Nodular regenerative hyperplasia of the liver, esophageal varices, and portal hypertension have been reported in patients receiving continuous busulfan and thioguanine therapy for the treatment of chronic myelogenous leukemia21.

Why it happens (mechanism)

Unknown

Literature reports

1 report — tap to read

a) Five patients with chronic myeloid leukemia receiving busulfan and thioguanine cotherapy developed esophageal varices 1. Of the four patients who underwent liver biopsies, all of them were diagnosed with nodular regenerative hyperplasia, which can result in esophageal varices, ascites, and splenomegaly. A preliminary analysis of 677 cases entered into the Medical Research Council's chronic myelogenous leukemia (CML) trial protocol (about half of which received combination therapy with busulfan and thioguanine) revealed 12 cases of esophageal varices. Nine of these patients presented with gastrointestinal bleeding, while the other three cases showed no clinical symptoms.

Common questions

Can I take Busulfan Injection and Thioguanine together?

An increased risk of nodular regenerative hyperplasia of the liver Always confirm with your pharmacist or prescriber before making any change.

How serious is the Busulfan Injection and Thioguanine interaction?

It is rated moderate. Can be significant — usually manageable with monitoring.

How quickly could this interaction happen?

The documented onset is "delayed". Effects tend to build up gradually over days to weeks.

How strong is the evidence for this interaction?

The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.

Questions for your pharmacist

  • Does my dose of Busulfan Injection or Thioguanine 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 anything you'd monitor while I'm on both?

References (2)

  1. Key NS, Kelly PMA, Emerson PM, et al: Oesophageal varices associated with busulfan-thioguanine combination therapy for chronic myeloid leukaemia. Lancet 1987; 2:1050-1052.
  2. Product Information: Tabloid(R), thioguanine. GlaxoSmithKline, Research Triangle Park, NC, 2004. 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:

Thioguanine + Activated Charcoal Coffee Charcoal European Mandrake Glucomannan Guar Gum Gum Arabic Slippery Elm Tragacanth + 9 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.