Busulfan

Busulfan is a cytotoxic chemotherapy agent in the alkylating class. It is a bifunctional alkylating agent that forms DNA cross-links, leading to cell death. Busulfan is available as an oral medication and as an intravenous formulation; the IV form is commonly used with pharmacokinetic monitoring to achieve a target level of systemic exposure.

In clinical practice, busulfan is primarily used as part of conditioning regimens before hematopoietic stem cell transplantation (HSCT). It is employed for diseases such as aplastic anemia, myelodysplastic syndromes, acute myeloid leukemia, and chronic myeloid leukemia. Busulfan is frequently combined with other agents, for example cyclophosphamide or fludarabine, and may be used with total body irradiation in some regimens.

Dosing and monitoring details vary by route and regimen. Oral busulfan has variable bioavailability, which can lead to unpredictable exposure. IV busulfan provides more consistent pharmacokinetics, and dosing is often individualized using pharmacokinetic monitoring to reach a target daily exposure. Typical regimens involve multiple daily doses given over several days as part of the conditioning protocol.

Adverse effects are dominated by myelosuppression and hepatotoxicity, including the risk of veno-occlusive disease. Seizures can occur, particularly with high-dose IV regimens, and prophylactic anticonvulsants are commonly used. Other possible toxicities include mucositis, nausea, pulmonary toxicity, infertility, and an increased risk of secondary malignancies. Dose adjustments and vigilant monitoring of liver function are important to minimize toxicity.

Brand names include Myleran (oral) and Busulfex (IV). Busulfan is contraindicated in pregnancy and used with caution in patients with significant hepatic impairment.