Bone marrow and peripheral blood stem cell transplantations, despite their curative potential, still carry significant risks for patients. Toxicity of high-dose chemotherapy is one of the leading causes of peritransplant mortality. Busulfan is a frequently used chemotherapeutic agent in conditioning regimens prior to transplantations. The choice of the optimal busulfan dose and prediction of its clinical effect may be very difficult. Absorption of busulfan from gastrointestinal tract and its metabolism can vary considerably. Several studies published recently showed that the busulfan plasma concentrations correlate better with the clinical effect and extramedullary toxicity caused by this drug than with the actual dose administered to the patient. Approximate target plasma concentrations of busulfan, which meet the optimal balance between the clinical effect and the risk of severe side effects of chemotherapy, were proposed. Almost twenty chromatographic methods were published, which make the quantitative measurement of busulfan possible. The maintanance of certain busulfan plasma concentration during its whole administration with the help of the repeated adjustments of its dosage can reduce the toxicity caused by this agent and improve the results of bone marrow or peripheral blood stem cell transplantations. This method is easily applicable, has low financal and personal demands, and technical appliances, which it requires are usually accessible in most transplant center laboratories.

        Key words: busulfan, pharmacokinetics, dose modifications, area under the curve, chromatography, bone marrow transplantation.