We evaluated the effect of age on cyclosporine pharmacokinetics in 69 nonobese patients aged 10 months to 56 years (median 22 years) undergoing allogeneic bone marrow transplantation for treatment of aplastic anemia or hematologic malignancy. Cyclosporine pharmacokinetics were studied during the first 2 posttransplant weeks after an intravenous dose of 2.6 to 3.5 mg/kg. Serum cyclosporine concentrations were measured by HPLC. Cyclosporine concentration-time data were fitted to a two-compartment model with a nonlinear regression program. There was a significant inverse linear correlation between age and both total systemic clearance (CL) (r = 0.42; P less than 0.001) and volume of distribution at steady-state (Vss) (r = 0.33; P less than 0.01). Mean (+/- SE) cyclosporine CL was 82 +/- 21, 45 +/- 5, 38 +/- 9, 44 +/- 8, and 20 +/- 3 ml/min/kg and mean cyclosporine Vss was 34 +/- 11, 28 +/- 10, 15 +/- 4, 14 +/- 5, and 4.7 +/- 0.7 L/kg in patients 0 to 10 (n = 12), 11 to 20 (n = 19), 21 to 30 (n = 12), 31 to 40 (n = 17), and greater than 40 (n = 9) years old, respectively. Patients 0 to 10 years old had a significantly higher cyclosporine CL than those 11 to 40 or greater than 40 years old and also had a significantly larger Vss than those greater than 40 yrs old (P less than 0.05). Age-related differences in CL or Vss were also observed when these parameters were normalized by body surface area.(ABSTRACT TRUNCATED AT 250 WORDS)

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