The pharmacokinetics of recombinant human erythropoietin in Balkan endemic nephropathy patients.

BACKGROUND Balkan endemic nephropathy (BEN) hemodialysis patients require a higher dose of recombinant human erythropoietin for maintaining target hemoglobin level than patients with other kidney diseases. OBJECTIVES Comparison of the pharmacokinetics of beta-erythropoietin given subcutaneously to hemodialysis patients with BEN or other kidney diseases (non-BEN). METHODS Recombinant human erythropoietin (75 U/kg) was administered subcutaneously to 10 BEN and 14 non-BEN hemodialysis patients. The predose plasma level of erythropoietin (Epo) was subtracted from all postdose levels. The relevant pharmacokinetic parameters were calculated after noncompartmental pharmacokinetic analysis using Kinetica software (Thermo Scientific, ver.5.0). RESULTS Although basal plasma Epo concentration was similar in BEN (20.1 ± 10.3 U/L) and non-BEN (15.1 ± 8.1 U/L; p=.1964) patients, there were significant differences between the groups for elimination rate constant (0.016 ± 0.006 vs 0.026 ± 0.011 hr⁻¹; p=.020) and elimination half-life (50.24 ± 19.12 vs 33.79 ± 18.91 hr, p=.048). These differences remained significant after adjustment for patient characteristics (age, sex, hemodialysis duration, ferritin, PTH and ACEI use). No significant differences between groups were found in maximal Epo concentration, time to maximum Epo concentration, area under the curve from time of dosing extrapolated to infinity, clearance, mean residence time of Epo between groups both before and after adjustment. CONCLUSION Pharmacokinetic analysis of beta-erythropoietin detected a significantly longer elimination half-life in BEN than in non BEN patients. This finding needs to be confirmed in a well-controlled study with a larger sample size.