Pharmacokinetic analysis of subcutaneous erythropoietin administration with nonlinear mixed effect model including endogenous production

Aims Erythropoietin, a glycoprotein hormone is produced by the kidney and targeted to erythrocyte precursors. Recombinant human erythropoietin (Epoetin beta) has been utilized for therapeutic purposes in renal anaemia or anaemia occurring after auto blood donation or chemotherapy. The administration routes for erythropoietin are normally subcutaneous or intravenous. No population pharmacokinetic analysis, however, has been performed following subcutaneous administration with consideration given for endogenous production. Methods In the present study, we have attempted to analyze the pharmacokinetics of erythropoietin after subcutaneous administration in healthy adult male volunteers by using the Nonlinear Mixed Effect Model program (NONMEM) with a model including endogenous erythropoietin production. Results It has been established that the final estimation of the population mean values of the absorption rate constant (k(a)), the elimination rate constant (k(e)), the distribution volume (V) and the endogenous production are 0.0430 h(-1), 0.206 h(-1), 3.141 and 15.7IU h(-1) respectively. For the circadian rhythm of endogenous production, the amplitude was calculated as 9.86% and the peak appeared around 24.00 h. Conclusions The values for k(e) and V are very similar to those previously reported for intravenous administration. The circadian rhythm of endogenous production are also able to be substantiated. The factors influencing k(e) were found to be serum creatinine and age.