Anemia is a low level of red blood cells (also called low hematocrit), or of hemoglobin, which is the oxygen-carrying part of the red blood cell. When the levels of red blood cells and/or hemoglobin decrease, the body has to work harder to carry oxygen to the cells, which can cause fatigue, muscle weakness, and difficulty breathing. People are diagnosed with anemia using a simple blood test that shows decreased amounts of hemoglobin in the blood. Normal levels of hemoglobin are 12 to 18 grams per deciliter (g/dL), with men naturally having slightly higher levels than women.
Depending on the reason for the anemia, it may be treated in a variety of ways. Doctors generally try to find the cause of anemia and reverse it, such as stopping internal bleeding, if it is the cause. Other specific treatments, such as iron, folate, or vitamin B6 or B12 supplements, can reverse anemia caused by nutritional deficiencies. Sometimes, while trying to find the cause, a red blood cell transfusion is used to replace blood for people who have symptoms or are very ill. Other times, epoetin or darbepoetin are used to increase blood cell production by the body.
Epoetin and darbepoetin are drugs that may help treat anemia caused by chemotherapy. They are similar to the hormone erythropoietin. Erythropoietin is made in the body naturally by the kidneys, and it helps the bone marrow produce more red blood cells in a process called erythropoiesis. For this reason, epoetin and darbepoetin are also called erythropoiesis-stimulating agents or ESAs. Epoetin and darbepoetin are given as a series of injections (shots) and can reduce the need for red blood cell transfusions and increase hemoglobin levels. However, these drugs also have risks, including the risk of serious or life-threatening blood clots. They have also increased the percentage of patients who died in some clinical studies. Furthermore, these drugs may increase tumor growth for some patients with cancer. In 2008, the FDA revised the drugs' labels to restrict the use of epoetin and darbepoetin to only those patients whose treatment is palliative (reducing the severity of symptoms to relieve a person's suffering); they should not be used for patients who are being treated in the hope of curing the cancer.