Erythropoiesis-stimulating agents

An erythropoiesis-stimulating agent (abbreviated ESA), also known as an erythropoiesis-stimulating drug (ESD) is a medicine similar to erythropoietin, which stimulates red blood cell production (erythropoeisis). ESAs, structurally and biologically, are similar to naturally occurring protein erythropoietin. They are used in conditions where reduced blood cell production causes anemia, such as advanced chronic kidney disease.

The following types of ESAs are available:

ESAs are used to maintain hemoglobin at the lowest level that both minimizes transfusions and best meets a person's needs. Medical speciality professional organizations do not recommend the use of ESAs in people with chronic kidney disease (CKD) who have hemoglobin levels greater than 10 g/dL and do not have anemia symptoms.

There is no evidence that one agent is better than another in the setting of CKD.

Recombinant erythropoietin has a variety of glycosylation patterns giving rise to alpha, beta, delta, and omega forms:

Darbepoetin alfa, which early literature during its development often termed as novel erythropoiesis-stimulating protein (NESP), is a form created by five substitutions (Asn-30, Thr-32, Val-87, Asn-88 and Thr-90) that create two new N-glycosylation sites. This glycoprotein has a longer terminal half-life, meaning it is possible to administer it less frequently.

Erythropoiesis-stimulating agents have a history of use as blood doping agents in endurance sports, such as horseracing, boxing,cycling, rowing, distance running, race walking, snowshoeing, cross country skiing, biathlon, Mixed Martial Arts and triathlon. The overall oxygen delivery system (blood oxygen levels, as well as heart stroke volume, vascularization, and lung function) is one of the major limiting factors to muscles' ability to perform endurance exercise. Therefore, the primary reason athletes may use ESAs is to improve oxygen delivery to muscles, which directly improves their endurance capacity. With the advent of recombinant erythropoietin in the 1990s, the practice of autologous and homologous blood transfusion has been partially replaced by injecting erythropoietin such that the body naturally produces its own red cells. ESAs increase hematocrit (% of blood volume that is red cell mass) and total red cell mass in the body, providing a good advantage in sports where such practice is banned. In addition to ethical considerations in sports, providing an increased red cell mass beyond the natural levels reduces blood flow due to increased viscosity, and increases the likelihood of thrombosis and stroke. Due to dangers associated with using ESAs, their use should be limited to the clinic where anemic patients are boosted back to normal hemoglobin levels (as opposed to going above the normal levels for performance advantage, leading to an increased risk of death).

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