Hydroxyurea is an oral chemotherapy drug that doctors may prescribe to people with sickle cell disease. It may help prevent complications due to sickle-shaped blood cells clumping together in small blood vessels.

Sickle cell disease is an inherited condition that affects the shape of red blood cells. Typical red blood cells are round, but in a person with sickle cell disease, they have a shape like a “c” or a farm tool called a sickle.

As sickle cells have shorter lifespans than typical red blood cells, a person with the condition will likely develop a chronic shortage of red blood cells. Sickle cells may also stick together and cause blockages in small blood vessels, which can lead to several complications.

A range of treatments, including hydroxyurea, may help prevent complications from sickle cell disease.

This article explores how hydroxyurea treats sickle cell disease, its risks and side effects, and how it may interact with other medications. The article also discusses other treatments for sickle cell disease and when someone should consider contacting a doctor.

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Hydroxyurea is an oral medication that prevents the formation of sickle cells by helping red blood cells stay flexible and round so that they can deliver oxygen throughout the body.

When sickle cell blood cells are deoxygenated, they begin to clump together and form chains, or long polymers. As polymers, sickle cells are also stickier. This stickiness increases the risk of blockages developing in small blood vessels, which can cause severe pain or a pain crisis, as well as organ damage and other complications.

Fetal hemoglobin (HbF) can prevent polymers from forming and, therefore, reduce the likelihood of blockages and organ damage from occurring. Hydroxyurea increases the amount of HbF in the blood, and this is how it prevents complications from sickle cell disease.

Doctors may refer to a pain crisis as a “vaso-occlusive episode (VOE).” VOEs can come on suddenly and range from mild to severe. The pain can develop in any part of the body, but people typically experience it in the hands, chest, back, and feet.

In adults, hydroxyurea often decreases the frequency of VOEs, improves anemia, and reduces the need for blood transfusions and hospital admissions. In children, the medication has similar outcomes but may also reduce swelling in the hands and toes.

However, researchers note that more studies are necessary to investigate the long-term use of hydroxyurea in people with sickle cell disease.

Both children and adults with sickle cell disease can take hydroxyurea. Pregnant people, however, cannot take hydroxyurea.

When people with sickle cell disease take hydroxyurea, they may develop a lower white blood cell or platelet count. Sometimes, their anemia symptoms may also worsen. However, this is rare.

Typically, these side effects disappear as soon as a person stops taking hydroxyurea. Other general side effects tend to affect the skin and gastrointestinal system.

Gastrointestinal side effects

These may include:

Skin side effects

These may include:

Long-term use of hydroxyurea may also increase a person’s chance of developing nonmelanoma skin cancers.

Hydroxyurea can interact with several medications. If someone is taking additional medications, their doctor will monitor them closely for hydroxyurea side effects and interactions with other drugs.

People with kidney problems may also require adjustments to their hydroxyurea dose. A healthcare professional may monitor a person’s kidney function and electrolyte levels while they are taking hydroxyurea.

If someone is taking HIV medication, such as didanosine or stavudine, hydroxyurea can increase the chance of serious and sometimes lethal liver toxicity and pancreas damage.

Healthcare professionals will likely recommend that a person stop taking hydroxyurea if they experience any symptoms of pancreatitis or liver toxicity.

Several medications treat sickle cell disease, including:

  • Voxelotor: This medication treats sickle cell disease in children and adults. Like hydroxyurea, it prevents red blood cells from taking on a sickle shape and sticking together.
  • Crizanlizumab-tmca: This drug prevents blood cells from sticking to blood vessel walls. This reduces VOEs and inflammation in children and adults.
  • L-glutamine: This medication helps reduce the number of VOEs in adults and children above the age of 5 years.
  • Lovotibeglogene autotemcel: The Food and Drug Administration (FDA) recently approved this gene therapy for individuals over the age of 12 years who have sickle cell disease and a history of VOEs. It is an intravenous infusion containing stem cells that prevent sickle cells from forming.

A doctor may also recommend penicillin to reduce the chance of blood infections. Additionally, a person may need blood transfusions to help treat complications.

Lastly, a bone marrow transplant can cure sickle cell disease. However, this procedure has many risks and is not suitable for everyone.

Healthcare professionals may also recommend a person make lifestyle changes, such as:

  • drinking plenty of water
  • avoiding becoming too cold or too hot
  • avoiding exposure to low oxygen levels, which may result from exercising too intensely or mountain climbing, for example
  • avoiding exposure to high altitudes

Healthcare professionals may also recommend maintaining good hygiene by washing hands frequently and preparing food correctly.

Some doctors may recommend that people taking hydroxyurea also take folic acid supplements. This is to prevent blood cells from enlarging as a result of hydroxyurea use.

Regardless of what medication a person is taking to manage their sickle cell disease symptoms, they should seek emergency medical care if they are experiencing:

Similarly, if a person is experiencing any side effects after taking hydroxyurea, it may be helpful to seek medical advice. A doctor may be able to change the dose or suggest an alternative medication.

Hydroxyurea can help prevent a range of sickle cell disease complications, including vaso-occlusive episodes. It works by making red blood cells more flexible and less likely to stick together.

However, hydroxyurea may cause side effects and can interact with other medications.

It is advisable for a person to speak with a doctor if they think they are experiencing side effects. The doctor may change the dose or recommend an alternative treatment.