Racial Differences in the Pharmacokinetics of Methylprednisolone in Black and White Renal Transplant Recipients

Study Objective . To examine the comparative pharmacokinetics of long-term methylprednisolone therapy in black and white renal transplant recipients. Design . Comprehensive pharmacokinetic evaluations of patients who participated in our glucocorticoid-monitoring program. Setting . University-based renal transplantation clinic. Patients . Six white renal transplant recipients with stable renal function, sex-and (approximate) age-matched with six preselected black patients. Interventions . The daily oral methylprednisolone dose for each patient was administered intravenously, and serial plasma samples were obtained over 24 hours. Measurements and Main Results . Methylprednisolone was analyzed by high-performance liquid chromatography. The drug's pharmacokinetics in black and white patients, respectively, were as follows: mean clearance 234 ± 124 and 472 ± 180 ml/hr/kg (p<0.05); volume of distribution 0.3-2.0 and 0.8-2.0 L/kg; and elimination rate constant 0.13-0.41 and 0.27-0.42 hour⁻¹ (p<0.06). No statistical difference was noted in the last two parameters. The mean half-life of 3.4 ± 1.4 hours in black patients compared with 2.1 ± 0.3 hours in white patients approached statistical significance (p<0.08). Conclusions . These preliminary observations suggest that the disposition of methylprednisolone differs between black and white renal transplant recipients. The current method of prescribing glucocorticoids employs a fixed-dose regimen that does not take these possible interracial differences into consideration. Incorporating the differences may allow for more individualized dosing and more efficacious use of the agent in this patient population.