Hydroxyurea for Sickle Cell Disease

Hydroxyurea has been used to treat sickle cell disease (SCD) since the 1980s. The U.S. Food and Drug Administration (FDA) approved it for treatment of adults with SCD in 1998 and treatment of children with SCD in 2017. It is also used to treat cancer, but at a higher dose than for SCD.

People with SCD benefit from hydroxyurea in many ways. It reduces the frequency of pain crises and hospitalizations, and can prevent other complications. It can also improve quality of life.

Hydroxyurea is the most common treatment for sickle cell disease.

What are the ingredients in hydroxyurea?

Hydroxyurea is the active ingredient.

How does it work?

The main way that hydroxyurea treats sickle cell disease is by increasing your amount of fetal hemoglobin (HbF). This type of hemoglobin is normally only present in newborns, and it protects them from complications of SCD. HbF is better than other types of hemoglobin at carrying oxygen around the body.1

Your amount of HbF decreases with age, and complications begin to occur without protection from HbF. Increasing HbF production with hydroxyurea helps prevent sickle hemoglobin from forming clumps inside red blood cells. This helps keep red blood cells round and flexible.2,3

Hydroxyurea also decreases production of white blood cells, especially a type of white blood cell called neutrophils. An elevated white blood cell count is linked to more severe outcomes of SCD. Lowering your white blood cell count can reduce sticking of red blood cells to other cells and blocking blood flow.1,4

Hydroxyurea also can release a chemical called nitric oxide. Nitric oxide helps to widen your blood vessels and improve blood flow.1

What are the possible side effects?

The most common side effects of hydroxyurea include:1,14

  • Headache
  • Abdominal discomfort and nausea
  • Enlarged red blood cells (macrocytosis)
  • Mild hair loss
  • Fingernail beds that turn darker

Other less common side effects include skin ulcers.1,14

These are not all the possible side effects of hydroxyurea. Talk to your doctor about what to expect or if you experience any changes that worry you.

Additional things to know

A common misconception is that hydroxyurea causes cancer. There is no evidence that hydroxyurea increases the risk of cancer in people with SCD, and it has been safely used since the 1980s. You can always talk to your doctor about any concerns regarding hydroxyurea.1,4,14
Most people take hydroxyurea pills once a day. Your doctor will prescribe a dosage that is right for you. They may start with a dose and perform regular blood tests to determine what dose works best for you. This includes tests to ensure that your:14

  • Hemoglobin levels go up
  • Red blood cells get bigger
  • Number of white blood cells (especially neutrophils) go down

Hydroxyurea is safe to take with most other medicines. However, tell your doctor about any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs. Hydroxyurea is not very expensive, and most health insurance plans cover it. Studies have also shown that taking hydroxyurea reduces total healthcare costs for people with SCD, mostly because of fewer hospital stays.15

Remember to take hydroxyurea every day. Missing a dose is not dangerous, but hydroxyurea works best if you take it every day. Hydroxyurea can sometimes take several months to a year to work.

If you are planning to have a baby, talk to your doctor. We still do not know how hydroxyurea affects your ability to have a healthy baby. With your doctor, you can decide whether or not to stop taking hydroxyurea. Some women choose to stop taking hydroxyurea early in pregnancy and then resume in the third trimester.14

For more information, read the full prescribing information of hydroxyurea.

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Written by: Matthew Zajac | Last reviewed: January 2021