What is erythropoietin?
Red blood cells are produced in the bone marrow (the spongy
tissue inside the bone). In order to make red blood cells, the body
maintains an adequate supply of erythropoietin (EPO), a hormone
that is produced by the kidney.
EPO helps make red blood cells. Having more red blood cells
raises your hemoglobin levels. Hemoglobin is the protein in red
blood cells that helps blood carry oxygen throughout the body.
Anemia is a disorder that occurs when there is not enough
hemoglobin in a person's blood. There are several different causes
of anemia. For instance, anemia can be caused by the body's
inability to produce enough EPO to make red blood cells. If this is
the case, the person may have to have a blood transfusion to treat
this type of anemia. If you have anemia, your physician can
determine the cause.
What is recombinant erythropoietin?
In cases where transfusions are not an option--for example,
when the patient cannot have, or refuses, a transfusion--it
may be necessary to give the patient recombinant erythropoietin.
Recombinant erythropoietin is a man-made version of natural
erythropoietin. It is produced by cloning the gene for
erythropoietin.
Recombinant erythropoietin drugs are known as
erythropoietin-stimulating agents (ESAs). These drugs are given by
injection (shot) and work by stimulating the production of more red
blood cells. These cells are then released from the bone marrow
into the bloodstream.
There are two ESAs on the U.S. market: epoetin alfa
(Procrit,® Epogen®), and darbepoietin alfa
(Aranesp®).
Who receives ESAs?
ESAs are usually given to patients who have chronic
(long-lasting) kidney disease or end-stage renal (kidney) disease.
These patients usually have lower hemoglobin levels because they
can't produce enough erythropoietin.
ESAs are also prescribed for patients who have cancer. These
patients often have anemia, which can be caused by
chemotherapy.
What are the side effects of ESAs?
The side effects that occur most often with ESA use include:
- High blood pressure
- Swelling
- Fever
- Dizziness
- Nausea
- Pain at the site of the injection.
What should the patient consider before using ESAs?
There are several safety issues with ESAs:
- ESAs increase the risk of venous thromboembolism (blood clots
in the veins). A blood clot can break away from one location and
travel to the lung (pulmonary embolism), where it can block
circulation. Symptoms of blood clots include chest pain, shortness
of breath, pain in the legs, and sudden numbness or weakness in the
face, arm, or leg.
- ESAs can cause hemoglobin to rise too high, which puts the
patient at higher risk for heart attack, stroke, heart failure, and
death.
- In patients who have cancer, ESAs may cause the tumor to grow.
If ESAs are used for these patients, they are usually stopped after
the patient's chemotherapy is finished.
- The health care provider will keep an eye on the
patient's blood cell counts to make sure they do not put him
or her at a higher risk. The dosing may change, depending on the
patient's needs.