Clinical pharmacokinetic studies of a human haemopoietic growth factor, GM-CSF

The pharmacokinetics of glycosylated recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) was studied following intravenous (i.v.) and subcutaneous (s.c.) bolus injection of rhGM-CSF, 8 micrograms kg-1 employing a sensitive radioimmunoassay. After a single i.v. bolus injection, an initial high serum level of rhGM-CSF was observed, followed by a rapid decrease that occurred in two phases with a half-life (t1/2) alpha of 20.0 +/- 5 min and a t1/2 beta of 68.3 +/- 8 min. Following s.c. bolus injection the absorption was more prolonged. Peak serum concentrations did not occur until about 15-20 h, and were followed by a more protracted elimination than by the i.v. route. In all patients the single rhGM-CSF injection led to an increase in peripheral white blood cells (WBC), after a temporary drop of 2-5 h duration. The increase in WBC was of longer duration after s.c. than after i.v. bolus treatment. Since the subcutaneous administration leads to prolonged serum concentration of rhGM-CSF and prolonged increase in peripheral WBC, it seems preferable to i.v. bolus injection, and as effective as continuous i.v. infusion.