Subcutaneous erythropoietin

Hematopoietic growth factors. Biology and clinical applications

The hematopoietic growth factors are potent regulators of blood-cell proliferation and development. The first phase of clinical trials suggests that they may augment hematopoiesis in a number of different conditions of primary and secondary bone marrow dysfunction. Future clinical use is likely to include combinations of these growth factors, in order to stimulate early marrow progenitors and obtain multilineage effects. An improved understanding of the biologic and clinical effects of hematopoietic growth factors promises future clinical applications for conditions of impaired function and reduced numbers of blood cells.

Recombinant human erythropoietin

Erythropoietin is produced mainly by the kidneys and stimulates erythropoiesis in the bone marrow. Chronic renal failure is characterized by anemia, which is principally caused by erythropoietin deficiency. Recombinant human erythropoietin (r-hEPO) corrects the anemia of chronic renal disease and improves patient well-being, exercise tolerance, and cognitive function. The clinical pharmacology, efficacy, safety, and tolerance of r-hEPO are presented. Four major studies attest to r-hEPO's efficacy in the treatment of anemia of chronic renal disease and document potential toxicities of hypertension, iron deficiency, thrombosis, and bone pain. Careful attention to the extent of correction of the hematocrit, increased heparinization during hemodialysis therapy, and compliance with dietary restrictions may minimize the incidence and severity of adverse reactions. Resistance to r-hEPO may be due to iron deficiency, aluminum toxicity, or inflammation, including infection. Potential future uses of r-hEPO include the treatment of various other anemias, such as those seen in sickle cell anemia, rheumatoid arthritis, and autologous blood donation. Controlled clinical studies in these areas have not been reported.

Pharmacokinetics of recombinant human erythropoietin in patients on continuous ambulatory peritoneal dialysis

To determine the optimum regimen for giving recombinant human erythropoietin (EPO) to patients on continuous ambulatory peritoneal dialysis (CAPD), the pharmacokinetics of single-dose EPO administered intravenously (120 U/kg), intraperitoneally (50,000 U), and subcutaneously (120 U/kg) was investigated. After intravenous administration serum EPO levels decayed exponentially from a peak of 3959 mU/ml, with a half-life of 8.2 h. 2.3% of the total intravenous dose was lost in the dialysate during the first 24 h. Peak serum EPO levels of 375 mU/ml at 12 h and 176 mU/ml at 18 h were attained following intraperitoneal and subcutaneous administration, respectively. The bioavailability of subcutaneous EPO (21.5%) was seven times greater than that of intraperitoneal EPO (2.9%). These results suggest that subcutaneous EPO represents the most satisfactory route of administration for CAPD patients.

Recombinant human erythropoietin in nephrology

rEPO therapy provides a unique opportunity to correct anemia in end-stage renal failure patients. Complete correction of the anemia, although possible, has some obvious disadvantages over a partial correction with a target hemoglobin of 10-13 g/dl or a hematocrit of 30-35%, respectively. Unresponsiveness to rEPO seems to be rare; in most cases the predicted hemoglobin increase could be seen as soon as an underlying iron deficiency was treated adequately. Blood loss and aluminum toxicity are the next most frequent reasons for an inadequate response to rEPO. Hypertension (and its complications) as well as fistula clotting are the most important side-effects which require close attention when patients at risk for these complications are treated with rEPO.