Busulfan is a chemotherapy drug, usually used to treat certain forms of leukemia. However, it is also used to prepare for a bone marrow transplant by suppressing the patient's existing bone marrow. Unlike most chemotherapy agents, it can be taken orally or intravenously. It is almost always used together with another drug, either to complement the effect of the other drug or to lessen its own side effects.

Side effects are atypical for a chemotherapy agent and include scarring of the lungs, seizures increase in pigmentation, occlusion of the veins of the liver and thrombocytopenia.

Busulfan at Wikipedia