Busulfan is the most common chemotherapy agent used in allogeneic hematopoietic cell transplant (HCT) conditioning regimens. As narrow therapeutic index and interpatient variability exists in the effectiveness and toxicity of conditioning regimens, personalizing intravenous busulfan therapy is desirable. Population pharmacokinetic-based approaches have been applied to therapeutic drug monitoring for the purpose of personalizing therapy. A population pharmacokinetic analysis with the objective of personalizing therapy in Japanese patients was conducted by integrating pediatric patient data with adult patient data. McCune's model, a 2-compartment model that includes maturation of clearance and allometric scaling of clearance and volume of distribution, was used for the analysis. McCune's model could precisely describe the Japanese data, and the estimated parameters were similar to McCune's results for non-Japanese, indicating that there are no racial differences in busulfan pharmacokinetics. Using this model, the plasma concentrations for once-daily dosing were simulated to adapt new dosage regimens for the benefit and convenience of both patients and medical staff. The predicted busulfan concentrations were within the therapeutic range.

The relationship between the kinds of drugs prescribed and age was investigated in 20990 outpatients (males; 11,716, females; 9,274) over the age of twenty at our hospital. No medicines for external application except for patch preparations for ischemic heart disease and injection preparations were caluculated in this studies. The following results were obtained: both preparation for the male and female outpatients increased with age. Although the mean kinds of drugs for patients in their twenties was 2.6, the mean kinds in patients in their eighties was 5.7. In addition, the number of outpatients with diabetes was increased significantly with age than in those without diabetes.

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