Highly toxic drug. The major adverse effect of busulfan is hematologic toxicity. Myelosuppression may manifest as leukopenia, thrombocytopenia, anemia, or any combination of these. Severe bone marrow suppression is common, resulting in possibly prolonged pancytopenia. Cardiac tamponade reported in children with thalassemia treated with high-dose oral busulfan in combination with cyclophosphamide. May produce hepatic veno-occlusive disease. Has been related with ovarian failure (including failure to achieve puberty) and amenorrhea. May cause delayed pulmonary toxicity («busulfan lung», a bronchopulmonary dysplasia with pulmonary fibrosis). Tumors and acute leukemias reported. Seizures reported (caution in patients predisposed to seizures, with history of seizures or head trauma). Dimethylacetamide, the solvent in I.V. busulfan, may impair fertility, and produce hepatotoxicity, hallucinations, somnolence, lethargy, and confusion. Reduction of dosage may be necessary with concomitant administration of other myelosuppressive agents. Hyperglycemia, hypomagnesemia, hypokalemia, hypocalcemia, and hypophosphatemia occur frequently in patients receiving I.V. busulfan. Infections, including sepsis and pneumonia, reported in patients receiving oral or I.V. busulfan.