Hydroxyurea is a medicine that is used to treat certain types of cancer as well as to reduce the frequency of pain crises and the need for blood transfusions in patients with sickle cell disease. Until recently, it was the only treatment option approved by the U.S. Food and Drug Administration (FDA) for the treatment of sickle cell disease. In July 2017, the FDA approved  Endari and in 2019 FDA approved Adakveo to treat the disease.

How does Hydroxyurea work?

Sickle cell disease is a disease in which abnormal hemoglobin protein causes the body to produce sickle- or crescent-shaped red blood cells. These cells have short lives compared to healthy, round red blood cells. The presence of sickle cells is linked to anemia — a condition where the blood cannot carry enough oxygen to the rest of the body.

Hydroxyurea works by increasing the level of a special type of hemoglobin called hemoglobin F (HbF) in the body. HbF is found at high levels in early stages of development. Compared to the adult form of hemoglobin, HbF is more effective in binding and carrying oxygen around the body. The increase of HbF production stimulated by hydroxyurea prevents the symptoms of anemia from developing.

Hydroxyurea studies

Several studies have investigated hydroxyurea as a treatment for sickle cell disease. Ample evidence suggests the therapy benefits patients with the disease. In fact, the FDA approved hydroxyurea as a treatment in 1998.

A review article published in the scientific journal Blood confirmed that hydroxyurea therapy has positive clinical outcomes for people with sickle cell disease. The review found that in 19 studies reporting data on blood, hydroxyurea therapy consistently increased HbF levels. It also confirmed that hydroxyurea benefited both children and adult patients with sickle cell disease and long-term treatment decreased mortality in symptomatic patients with the disease when compared to patients who had received shorter-term hydroxyurea treatment, or no treatment with this drug.

Additional information

The full benefits of hydroxyurea may take months to develop, and its benefits also depend on the right dosage in an individual. In addition, hydroxyurea works only by affecting blood that is made in the bone marrow on the day the drug is taken. For some patients, the therapy may even take up to a year to establish or get the right dosage right and reap benefits.

Hydroxyurea can severely decrease the number of blood cells in the bone marrow. It may also increase the risk of serious infections or bleeding.


Last updated: Feb. 21, 2020


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