Hydrea (Hydroxyurea) - Oral

What Is Hydrea?

Hydrea (hydroxyurea) is an antimetabolite medication used to treat chronic myeloid leukemia and locally advanced squamous cell head and neck carcinomas. It may be used alone or combined with other therapies. Hydroxyurea is also used in sickle cell disease to reduce the frequency of painful crises and the need for blood transfusions.

This medication interferes with the production of cancer cells by disrupting the formation of deoxyribonucleic acid (DNA) molecules. It specifically inhibits ribonucleotide reductase, an enzyme involved in DNA synthesis.

In sickle cell disease, hydroxyurea makes your red blood cells bigger, which allows them to keep their normal, round shape. It also increases hemoglobin F or fetal hemoglobin. Having higher amounts of this type of hemoglobin can reduce the complication associated with sickle cell disease.

It is approved for adults and available by prescription in capsule form to be taken orally. Hydroxyurea is available under two brand names: Hydrea and Droxia, and as a generic medication.

Drug Facts

Generic Name: Hydroxyurea

Brand Name(s): Hydrea, Droxia

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antineoplastic agent

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Hydroxyurea

Dosage Form(s): Tablet, capsule

What Is Hydrea Used For?

Hydrea is used to treat certain types of cancer. It can be used alone or in conjunction with other cancer treatments, such as radiation or chemotherapy. It is also used to decrease the rate of painful episodes in sickle cell disease.

The Food and Drug Administration (FDA) approved hydroxyurea to treat:

  • Resistant chronic myeloid leukemia (CML): Also called chronic myelogenous leukemia, CML is a type of cancer caused by the overproduction of abnormal white blood cells in the bone marrow. It is more common in adults than children. It may spread throughout the body and can cause fatigue and frequent infections. This type of cancer can progress rapidly or slowly. 
  • Locally advanced squamous cell carcinomas (SCC) of the head and neck, (excluding lip) in combination with concurrent chemoradiation: Squamous cell carcinoma is a type of skin cancer that can be highly aggressive. It may spread locally (in the adjacent tissues) and can sometimes metastasize (spread to distant parts of the body).
  • Sickle cell disease: In sickle cell disease, the red blood cells contain abnormal hemoglobin (a protein that carries oxygen), which can lead to many complications. Hydroxyurea can be used in adults and children 2 years and older with sickle cell anemia with recurrent moderate to severe painful crises. A sickle cell crisis is an episode characterized by severe pain that can come on suddenly and last several hours to days. Hydroxyurea can also reduce episodes of acute chest syndrome, blood transfusions, and hospitalization.

How to Take Hydrea

The prescribed dosage of Hydrea is based on several factors, including the type and stage of cancer. You can take Hydrea with or without food. The capsules should be swallowed whole; do not chew, break, or open them.

Healthcare providers usually prescribe a lower amount for sickle cell disease than for cancer. Take your medication as prescribed, usually once a day. You will need regular blood cell count monitoring during your treatment.

Due to its cytotoxic nature, this medication should be handled cautiously by you or your caregiver. Wear gloves while giving or taking it to avoid direct contact. While on this medication, your healthcare team may monitor blood counts at least once weekly.


Hydrea should be kept in its original container, tightly closed, and out of reach of children or pets. It should be stored at a temperature (between 68 F and 77 F). You can temporarily expose it to temperatures as low as 59 F and as high as 86 F.

This medication is a cytotoxic drug, which means it has special rules for handling and disposal. It is important to minimize direct contact with Hydrea; therefore, a person should wear gloves while handling Hydrea or bottles containing Hydrea. Wash hands before and after giving or taking the medication. Ask your oncology care team how to best dispose of any unused medication.

How Long Does Hydrea Take to Work?

Hydrea reaches peak plasma levels about one to four hours after a dose. You must take this medication consistently and as prescribed for it to be effective. Follow up with your healthcare provider regularly; they will monitor your progress and response to treatment.

What Are the Side Effects of Hydrea?

This medication can cause several mild side effects, as well as potentially dangerous side effects. Therefore, you must familiarize yourself with these potential reactions so you know when to receive medical attention.

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 1-800-FDA-1088.

Common Side Effects

The most common side effects of Hydrea are:

  • Decreased appetite 
  • Low white blood cell count (leukopenia), low red blood cell count (anemia), or low platelet count (thrombocytopenia)
  • Nausea or vomiting
  • Diarrhea 
  • Rash

Talk to your healthcare provider if you develop any of these issues. You might benefit from symptomatic treatment to help manage any adverse reactions to therapy.

Severe Side Effects

Hydrea can also cause potentially dangerous adverse effects that might necessitate a change or discontinuation of your treatment.

Call your healthcare provider immediately if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects can include the following:

  • Myelosuppression (decreased production of healthy blood cells in the bone marrow) 
  • Blood vessel inflammation or damage 
  • Severe hypersensitivity reaction, with a fever, rash, and organ involvement 
  • Birth defects if taken during pregnancy

Hydrea can also cause a side effect called macrocytosis, which often manifests early in treatment. Macrocytosis resembles pernicious anemia, although it unrelated to vitamin B12 or folic acid deficiency. Because of this, it can mask a diagnosis of pernicious anemia. Your healthcare provider may recommend folic acid supplementation as a preventive strategy.

Your healthcare team will monitor you for early signs of these problems while taking Hydrea. Urgent treatment might be necessary if severe side effects arise.

Long-Term Side Effects

After using Hydrea, there is a prolonged risk of developing another primary cancer. However, this risk will decline over time.

Anyone who uses Hydrea can be at risk of infertility or congenital disabilities in their offspring. It's important to discuss your conception and pregnancy plans with your healthcare provider before starting Hydrea. One option is to preserve your eggs or sperm before treatment through methods such as egg freezing and sperm banking.

Report Side Effects

Hydrea may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Hydrea Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For cancer of the head and neck:
    • For oral dosage form (capsules):
      • Adults—Dose is based on body weight and must be determined by your doctor. The dose is 15 milligrams (mg) per kilogram (kg) of body weight per day, taken as a single dose. Your doctor may adjust your dose as needed.
      • Children—Use and dose must be determined by your doctor.
  • For chronic myelocytic leukemia (CML):
    • For oral dosage form (capsules):
      • Adults—Dose is based on body weight and must be determined by your doctor. The dose is 15 milligrams (mg) per kilogram (kg) of body weight per day, taken as a single dose. Your doctor may adjust your dose as needed.
      • Children—Use and dose must be determined by your doctor.
  • For sickle cell anemia:
    • For oral dosage form (capsules):
      • Adults—Dose is based on body weight and must be determined by your doctor. At first, the dose is 15 milligrams (mg) per kilogram (kg) of body weight per day, taken as a single dose. Your doctor may adjust your dose as needed. However, the dose is usually not more than 35 mg per kg of body weight per day.
      • Children—Use and dose must be determined by your doctor.
    • For oral dosage form (tablets):
      • Adults—Dose is based on body weight and must be determined by your doctor. At first, 15 milligrams (mg) per kilogram (kg) of body weight once a day. Your doctor may adjust your dose as needed.
      • Children 2 years of age and older—Dose is based on body weight and must be determined by your doctor. At first, 20 mg per kg of body weight once a day. Your doctor may adjust your dose as needed.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor.


Due to the possible effects of this medication, there may be changes to how it is used. Therefore, users need to be aware of the following when taking Hydrea:

  • Kidney disease: You may need a dose reduction of Hydrea if you have advanced kidney disease or limited kidney functioning. Dialysis may also affect when you should take your dose. Consult with your healthcare provider if you have kidney problems.
  • Protection against pregnancy: If you can conceive and become pregnant, it's important to take precautions to prevent pregnancy while on this medication and for at least six months after stopping it. Males of reproductive potential with partners who can conceive should use contraception during and after treatment for at least one year.
  • Breastfeeding: Do not breastfeed while using Hydrea.

If you are taking hydroxyurea for sickle cell disease, your healthcare provider might adjust your dose based on your blood cell counts.

Missed Dose

If you miss a dose, take it as soon as you remember. If it is too close to your next dose, skip the missed dose and return to your regular dosing schedule.

Keep track of all missed doses and notify your healthcare team about the missed doses at your next visit.

Overdose: What Happens If I Take Too Much Hydrea?

Taking too much Hydrea can cause severe problems, including:

  • Acute mucocutaneous toxicity (toxicity to the skin and membranes)
  • Soreness 
  • Purple skin 
  • Redness of the skin 
  • Swelling of palms and soles 
  • Scaling on the hands and feet 
  • Rapidly darkened skin 
  • Sore throat

Your healthcare provider will closely monitor your symptoms and may give you symptomatic treatment for the effects of an overdose.

What Happens If I Overdose on Hydrea?

If you think you or someone else may have overdosed on Hydrea, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Hydrea, call 911 immediately.


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It is very important that your doctor check your or your child's progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. If you are a woman who can get pregnant, your doctor may do tests to make sure you are not pregnant before starting this medicine. Women should use an effective form of birth control during treatment with this medicine and for at least 6 months after the last dose. Men should use an effective form of birth control during treatment and for at least 1 year for Droxia® and Hydrea® and at least 6 months for Siklos® after the last dose to prevent pregnancy in a sexual partner. If a pregnancy occurs while using the medicine, tell your doctor right away.

Hydroxyurea can temporarily lower the number of white blood cells in your blood which increases the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

  • If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
  • Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
  • Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
  • Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
  • Avoid contact sports or other situations where bruising or injury could occur.

Check with your doctor right away if you have back, leg, or stomach pains, bleeding gums, chills, dark urine, difficulty breathing, fever, general body swelling, headache, loss of appetite, nausea or vomiting, nosebleeds, pale skin, sore throat, unusual tiredness or weakness, or yellowing of the eyes or skin. These may be symptoms of a blood problem called hemolytic anemia.

Using this medicine for a long time may increase your risk of developing leukemia (cancer of the blood) or skin cancer. Use a sunscreen and protective clothing to protect your skin. Talk to your doctor if you have concerns about this risk.

If you had radiation treatment in the past, Hydrea® may cause your skin to become very red when you have radiation again. Tell your doctor right away if you have darkening or reddening of the skin.

While you are being treated with hydroxyurea, do not have any immunizations (vaccinations) without your doctor's approval. Live virus vaccinations (eg, nasal flu virus vaccine) should not be given while you are using hydroxyurea.

This medicine may increase your risk of having lung or breathing problems (eg, interstitial lung disease). Check with your doctor right away if you develop a fever, cough, or trouble breathing while using this medicine.

Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before you have medical tests.

Talk with your doctor before using this medicine if you plan to have children. Some men who use this medicine have become infertile (unable to have children).

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Hydrea?

You shouldn't take Hydrea if any of the following apply to you:

  • You are pregnant: This medication is toxic to fetal development. Avoid becoming pregnant while taking it. If you become pregnant while on Hydrea, stop taking it immediately and contact your healthcare provider.
  • You are breastfeeding: You should not breastfeed while taking Hydrea due to its toxicity.
  • You are allergic to hydroxyurea or any of its ingredients

You will need to stop taking Hydrea if you:

  • Become pregnant during treatment
  • Experience vasculitic toxicities
  • Have persistent hemolytic anemia

What Other Medications Interact With Hydrea?

Hydrea can interact with several treatments, potentially causing adverse effects.

For instance, taking Hydrea with antiretroviral drugs, which are used for treating HIV infection, can cause:

  • Hepatotoxicity (liver damage) and hepatic failure with symptoms of yellowish skin, yellow discoloration of the whites of your eyes, and dark urine
  • Pancreatitis with fever, fatigue, nausea, and vomiting 
  • Peripheral neuropathy with numbness, tingling, and pain in the hands and feet

Additionally, taking Hydrea with radiation treatment can trigger skin redness and inflammation.

This is not a complete list of drug interactions that can occur with Hydrea. Be sure to communicate your use of prescription and OTC medicines, vitamins, and herbal supplements with your oncology healthcare provider to avoid any potential interactions.

Another consideration is immunization, as receiving live vaccines is not recommended while using Hydrea. Doing so may result in infection from the living organism in the vaccine. However, you can receive vaccines that do not contain a live pathogen (infectious virus or bacteria).

Examples of live vaccines to avoid include:

  • Measles, mumps, and rubella (MMR combined vaccine)
  • Rotavirus
  • Smallpox
  • Chickenpox
  • Yellow fever
  • Nasal spray flu vaccine

Other nonlive vaccines, such as the COVID-19 vaccine and the inactivated flu vaccines, are OK to receive.

What Medications Are Similar?

Similar to hydroxyurea, many chemotherapeutic treatments disrupt DNA production through different mechanisms.

Other therapeutics used to treat CML include:

  • Mylocel (hydroxycarbamide)
  • Gleevec (imatinib)
  • Sprycel (dasatinib)
  • Tasigna (nilotinib)
  • Bosutinib

Frequently Asked Questions

  • What is Hydrea used for?

    Hydrea is a chemotherapeutic medication used to treat resistant chronic myeloid leukemia, or CML, and locally advanced squamous cell carcinoma of the head and neck. It is also used off-label to treat sickle cell disease.

  • How does Hydrea work?

    Hydrea prevents production of cancer cells by interfering with an enzyme that is involved in DNA synthesis. DNA synthesis is a major step in the production of all cells, including cancer cells.

  • What drugs should not be taken with Hydrea?

    You should not get any live vaccines while you are taking Hydrea. Additionally, using Hydrea with antiretroviral drugs (used to treat HIV infection) or radiation therapy would be done with caution.

  • How long does it take for Hydrea to work?

    This medication reaches its peak concentrations in the body in one to four hours. However, it can take weeks before it has a measurable therapeutic effect on cancer or sickle cell disease. 

  • What are the side effects of Hydrea?

    This medication can cause appetite loss, gastrointestinal (GI) symptoms, and blood-related problems. Less often, it can also cause a severe hypersensitivity reaction, an increased risk of cancer, infertility, and birth defects.

  • How do I safely stop taking Hydrea?

    You should stop taking Hydrea when the full course prescribed by your healthcare provider is completed. Let your healthcare provider know if you experience side effects. You might need to have your treatment adjusted.

How to Stay Healthy While Taking Hydrea

While taking Hydrea, you may develop appetite changes or GI-related side effects. If this happens, talk to your healthcare provider about an eating plan or prescription supplement use to ensure you are getting proper nutrition. You may also be prescribed folic acid to take while you are on Hydrea to prevent a side effect called macrocytosis (enlarged red blood cells).

Hydrea can temporarily lower your white blood cell count, which can make you prone to getting infections. Avoid exposure to illness if possible, and consider wearing a face mask in crowded places.

You may be taking other medications at the same time. Be sure to communicate with your healthcare team if you experience any bothersome side effects. Do not change your medication regimen without talking to a healthcare provider.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.