Pharmacokinetics of recombinant human erythropoietin in chronic haemodialysis patients.

Single dose intravenous and subcutaneous pharmacokinetics of recombinant human erythropoietin (rhEPO) has been determined in 6 chronic haemodialysis patients. Four patients, all on maintenance therapy with rhEPO, were consecutively treated both intravenously and subcutaneously with injections of rhEPO in a dose of 50 U/kg. Two previously untreated patients received 150 U/kg of rhEPO intravenously and subcutaneously. After intravenous injection of 50 U/kg of rhEPO a mean serum half-life value of 5.4 +/- 0.9 hr was found. The corresponding half-life after injection of 150 U/kg was 7.6 hr. The peak concentration of serum EPO after subcutaneous injection was 12.5-20 times lower than the corresponding intravenous Cmax. After administration of 150 U/kg subcutaneously the absorption of EPO was monitored to completion at 120 hr. The complete bioavailability of subcutaneous rhEPO after injection of 150 U/kg was 31.7%. Whether this low and protracted subcutaneous absorption of rhEPO is accounted for by either impeded absorption or partial skin degradation of rhEPO is not known.