What is hydroxyurea, and how does it work (mechanism of action)?

Hydroxyurea (Hydrea) is an oral medication used to treat several types of cancers including chronic myelogenous leukemia (CML), acute myelogenous leukemia (AML), head and neck cancer, malignant melanoma, ovarian cancer, and polycythemia vera (a disorder of the bone marrow). The exact mechanism by which hydroxyurea works to treat cancer is not understood. However, it is thought that hydroxyurea causes an immediate inhibition of DNA synthesis by inhibiting an enzyme called ribonucleotide reductase. Interrupting DNA synthesis reduces the growth of cancer cells.

In-addition to treating cancer, Droxia another oral form of hydroxyurea is used in the management of sickle cell disease. The exact mechanism by which hydroxyurea works to treat sickle cell disease is not understood. The FDA approved hydroxyurea in December 1967.

What brand names are available for hydroxyurea?

Hydrea, Droxia

Is hydroxyurea available as a generic drug?


Do I need a prescription for hydroxyurea?


What are the side effects of hydroxyurea?

Known side effects include:

What is the dosage for hydroxyurea?

For treating cancer: Dose should be titrated based on individual patient response. Capsules should be swallowed whole. Hydroxyurea capsules should be handled with extreme care and disposed of properly because it causes cell damage.

For the treatment of solid tumors

  • Intermittent therapy: 80 mg/kg administered orally as single dose every third day
  • Continuous therapy: 20 to 30 mg/kg administered orally as a single daily dose
  • Concomitant therapy with irradiation: Cancer of the head and neck, administer 80 mg/kg orally as a single dose every third day

For the treatment of chronic myelocytic leukemia

20 to 30 mg/kg administered orally as a single daily dose is recommended.

As hydroxyurea is mainly eliminated from the body via the kidneys, dose reductions may be necessary in patients with reduced kidney function.

For the treatment of sickle cell disease

Adults: administer 15 mg/kg by mouth once daily. Dose adjustments are made based on patient’s blood counts. Patient’s blood counts are monitored every two weeks. If the blood counts are in an “acceptable” range, the dose may be increased by 5 mg/kg/day every 12 weeks until a maximum tolerated dose (highest dose that does not produce toxic blood counts) or 35 mg/kg/day is reached.

Which drugs or supplements interact with hydroxyurea?


Generally, use of live vaccines is contraindicated during treatment with cancer drugs because cancer drugs weaken the immune system. People with weakened immune systems have a decreased response to vaccines.

Hydroxyurea may cause a drop in platelet counts, an important type of blood cells required for forming blood clots. Use of hydroxyurea with anticoagulants, nonsteroidal anti-inflammatory drugs (NSAIDs), antiplatelets, and thrombolytic agents increases the risk of bleeding.

Antineoplastic agents exert their benefits by killing rapidly growing cancer cells. Use of medications that stimulate cell growth is usually not recommended in patients who have been exposed to cytotoxic chemotherapy within 24 hours. Specifically, the manufacturer of pegfilgrastim (Neulasta) recommends that pegfilgrastim should not be administered to patients who have been treated with cytotoxic chemotherapy within the prior 14 days. Also, chemotherapy should not be administered within 24 hours of pegfilgrastim.

Hydroxyurea may increase blood uric acid concentration. Although no specific dose adjustments are necessary with probenecid or sulfinpyrazone (Anturane), hydroxyurea should be used cautiously with uricosuric medications.

Use of hydroxyurea with didanosine (Videx, Videx EC), with or without stavudine (Zerit, Zerit XR), has been associated with an increased incidence of side effects including pancreatitis and peripheral neuropathy (nerve problems). In general, hydroxyurea is not recommended in HIV patients as decreased CD4 counts, decreased viral suppression, and increased risk of side effects has been reported.

From WebMD Logo

Cancer Resources
Featured Centers
Health Solutions From Our Sponsors

Is hydroxyurea safe to take if I’m pregnant or breastfeeding?

Hydroxyurea can cause harm to the unborn baby and therefore, should not be used during pregnancy. Although there are no adequate and well-controlled studies in pregnant women, in animals studies hydroxyurea was found to cause birth defects.

Hydroxyurea is secreted in human milk. Nursing should be stopped due to the potential for serious adverse reactions in the infant.

What else should I know about hydroxyurea?

What preparations of hydroxyurea are available?
  • Hydrea: 500 mg capsules. Hydrea is used an antineoplastic agent.
  • Droxia: 200 mg, 300 mg, 400 mg capsules. Droxia is used to treat sickle cell disease.
How should I keep hydroxyurea stored?

Capsules should be stored at room temperature between 59 F to 86 F (15 C to 30 C).

Medically Reviewed on 3/18/2019


Medically reviewed by John P. Cunha, DO, FACOEP; Board Certified Emergency Medicine


FDA Prescribing Information.