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Common and Serious Busulfan Side Effects

Megan N. Freeland, PharmD
January 18, 2021

Myelosuppression is one of the most common side effects of busulfan. In its role as part of a conditioning regimen prior to hematopoietic stem cell transplant (HCT), this side effect is actually being intentionally exploited. During the pretransplant period, the purpose of busulfan is to ablate the body’s bone marrow cells in order to lay the groundwork for receiving the transplanted donor cells.

But while bone marrow suppression is a desired effect of busulfan in this clinical scenario, busulfan has side effects that can be problematic.

You may have read about some of busulfan’s side effects previously. Here, we’ll dive a bit deeper into the side effect profile of busulfan, including common and serious potential side effects.

Common busulfan side effects

Since it’s a cytotoxic drug, you’d probably expect that patients receiving busulfan will experience some side effects. In clinical trials, the most common injectable busulfan side effects, in addition to myelosuppression, were:

  • Nausea, vomiting, diarrhea
  • Abdominal pain
  • Mucositis or stomatitis
  • Anorexia
  • Insomnia
  • Fever
  • Hypomagnesemia, hypokalemia
  • Hyperglycemia
  • Headache
  • Anxiety 

In trials, the incidence of most of these side effects was upwards of 50%. Some side effects—particularly, the GI side effects, electrolyte imbalances, fever, and headache—occurred in 65% to 80% of trial participants. 

Serious busulfan side effects

While the common side effects can be bothersome and present concerns for patients and their treating clinicians, the more serious side effects associated with busulfan pose even more risks. Examples of these serious busulfan side effects include:

  • Arrhythmia
  • Atrial fibrillation
  • Cerebral hemorrhage
  • Left-sided heart failure
  • Graft-versus-host disease (GVHD)
  • Pancreatitis
  • Cardiomegaly 
  • Hemorrhagic cystitis
  • CMV viremia
  • Hepatic sinusoidal obstruction syndrome (SOS)

We’ve provided more details regarding GVHD, hepatic SOS, CMV viremia, hemorrhagic cystitis, and mucositis, but it’s important to understand that a multitude of other risks exist.

Reducing the risk of busulfan lung injury and related toxicities

Of all the potential adverse events a person taking busulfan may experience, the drug is most notorious for potential pulmonary toxicity. In fact, busulfan was one of the first cytotoxic drugs to be linked to pulmonary toxicity, causing conditions like chronic interstitial pulmonary fibrosis, and even acute lung injury or alveolar hemorrhage.

As clinicians consider how to best prepare their patients for HCT—aiming to maximize transplant success—they are also aiming to mitigate the risk of adverse events. The dosing regimens they develop are done so with these priorities in mind.

Precision dosing software is a supportive, complementary technological tool that helps clinicians strike this critical balance between efficacy and safety. 

Learn more about balancing the rewards and risks of busulfan therapy in our white paper.


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