Busulfan (Busulfex) — Clinical FAQs

Question 1

What is Busulfan FDA-approved to treat?

Accepted Answer

Busulfan is FDA-approved for the following oncology indications: 1. Chronic myelogenous leukemia (CML) — palliative treatment (oral Myleran; FDA approved 1954) 2. Conditioning regimen for allogeneic hematopoietic stem cell transplantation (IV Busulfex; FDA approved 1999, pivotal multicenter phase II trial).

Question 2

How does Busulfan work (mechanism of action)?

Accepted Answer

Busulfan is a bifunctional alkyl sulfonate that acts as a bifunctional alkylating agent, forming carbonium ion intermediates that alkylate DNA at the N7 position of guanine, creating interstrand DNA crosslinks that inhibit DNA replication and transcription. Unlike nitrogen mustards, busulfan preferentially alkylates thiol groups on intracellular proteins in addition to DNA. It demonstrates selective toxicity toward hematopoietic stem cells at low doses (CML treatment) and myeloablative activity at high doses (HSCT conditioning). It is cell-cycle nonspecific.

Question 3

How is Busulfan administered?

Accepted Answer

Busulfan is administered Intravenous (IV) or Oral (PO). IV (HSCT conditioning): 0.

Question 4

What are the most common side effects of Busulfan?

Accepted Answer

The most commonly reported side effects of Busulfan (≥10% incidence) include: Severe myelosuppression (neutropenia, thrombocytopenia, anemia) — universal with high-dose, Nausea, vomiting, mucositis (high-dose), Hepatotoxicity (transaminase elevation), Skin hyperpigmentation (busulfan tan) with chronic oral use, Diarrhea and others (10 total). Consult your oncologist for complete prescribing information.

Question 5

Does Busulfan have a black box warning?

Accepted Answer

Yes. Busulfan carries FDA black box warning(s) regarding: 1. Severe myelosuppression — may result in irreversible bone marrow failure at high doses; used intentionally for myeloablative HSCT conditioning 2. Seizures — busulfan lowers seizure threshold; seizure prophylaxis with anticonvulsants is required for IV high-dose regimens 3. Hepatic veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS) — potentially fatal; higher risk with high-dose IV regimens 4. Embryotoxic and teratogenic — avoid use in pregnancy

Question 6

Is Busulfan safe during pregnancy?

Accepted Answer

Busulfan pregnancy safety: Category D — busulfan is embryotoxic and teratogenic. Several cases of human fetal abnormalities reported. Avoid during pregnancy; women of childbearing potential must use effective contraception during and after therapy.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Busulfan — Drug Monograph

Mechanism of Action

FDA Indications

Common Side Effects

Clinical Pearl

Related Therapies & Mechanisms