Hydroxyurea is a medicine 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 recent years, it was the only treatment approved by the U.S. Food and Drug Administration (FDA) specifically for sickle cell. The FDA approved  Endari in July 2017, followed by Adakveo in 2019 to treat people with this disease.

How does Hydroxyurea work?

In sickle cell disease, abnormal hemoglobin protein causes the body to produce sickle- or crescent-shaped red blood cells. Sickle cells often stick to blood vessel walls, blocking or slowing blood flow and oxygen transport. The presence of sickle cells is linked to anemia — a condition where the blood cannot carry enough oxygen to the rest of the body.

These cells also have shorter lives compared to healthy, round red blood cells.

Hydroxyurea works by increasing the level of a special type of hemoglobin called hemoglobin F (HbF). 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, and ample evidence suggests the therapy benefits patients with the disease. The FDA approved hydroxyurea as a treatment for adult patients 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 depend on the proper dose given an individual. Hydroxyurea works  by affecting blood that is made in the bone marrow on the day  it is taken. For some patients, the therapy can take up to a year to establish the right dose and notice its 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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