Hydroxyurea can cause a severe decrease in the number of blood cells in your bone marrow. This may increase the risk that you will develop a serious infection or bleeding. If you experience any of the following symptoms, call your doctor immediately: fever, chills, excessive tiredness or weakness, body aches, sore throat, shortness of breath, ongoing cough and congestion, or other signs of infection; unusual bleeding or bruising; bloody or black, tarry stools; or vomiting blood or brown material that resembles coffee grounds.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain tests on a regular basis to check your body’s response to hydroxyurea and to see if your blood count has dropped. Your doctor may need to change your dose or tell you to stop taking hydroxyurea for a period of time to allow your blood count to return to normal if it has dropped too low.

Hydroxyurea may increase the risk that you will develop other cancers, including skin cancer. Plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Talk with your doctor about the risks of taking hydroxyurea.

Your doctor or pharmacist will give you the manufacturer’s patient information sheet (Medication Guide) when you begin treatment with hydroxyurea and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visit the Food and Drug Administration (FDA) website (http://www.fda.gov/Drugs/DrugSafety/ucm085729.htm) to obtain the Medication Guide.

Hydroxyurea (Hydrea) is used alone or with other medications or radiation therapy to treat a certain type of chronic myelogenous leukemia (CML; a type of cancer of the white blood cells) and certain types of head and neck cancer (including cancer of the mouth, cheek, tongue, throat, tonsils, and sinuses). Hydroxyurea (Droxia, Siklos) is used to reduce the frequency of painful crises and reduce the need for blood transfusions in adults and children 2 years of age and older with sickle cell anemia (an inherited blood disorder in which the red blood cells are abnormally shaped [shaped like a sickle] and cannot bring enough oxygen to all parts of the body). Hydroxyurea is in a class of medications called antimetabolites. Hydroxyurea treats cancer by slowing or stopping the growth of cancer cells in your body. Hydroxyurea treats sickle cell anemia by helping to prevent formation of sickle-shaped red blood cells.

Hydroxyurea comes as a capsule and tablet to take by mouth. It is usually taken once a day with a glass of water. When hydroxyurea is used to treat certain types of cancer, it may be taken once every third day. Take hydroxyurea at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take hydroxyurea exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor may need to delay your treatment or adjust your dose of hydroxyurea depending on your response to treatment and any side effects that you may experience. Talk to your doctor about how you are feeling during your treatment. Do not stop taking hydroxyurea without talking to your doctor.

Your doctor will probably tell you to take another medication, folic acid (a vitamin), to decrease some of the side effects of this medication. Take this medication exactly as directed.

Swallow the capsules whole; do not split, chew, or crush them.

The hydroxyurea 1,000-mg tablets (Siklos) are scored so that they can easily be split into halves or quarters to provide smaller doses. Do not break the hydroxyurea 100-mg tablets into smaller parts. Your doctor will tell you how to break the tablets and how many tablets or parts of a tablet you should take.

If you are unable to swallow hydroxyurea tablets or portion(s) of tablets, you may dissolve your dose in water. Place your dose in a teaspoon and add a small amount of water. Wait about 1 minute to allow the tablet(s) to dissolve, then swallow the mixture right away.

You should wear rubber or latex gloves when you handle the capsules or tablets so that your skin does not come into contact with the medication. Wash your hands with soap and water before and after you touch the bottle or medication. If hydroxyurea gets into your eyes, immediately flush your eyes with water for at least 15 minutes. If the powder from a capsule or tablet spills, wipe it up immediately with a damp disposable towel. Then place the towel in a closed container, such as a plastic bag, and throw it away in a trash can that is out of the reach of children and pets. Clean the spill area using a detergent solution followed by clean water.

Hydroxyurea is also sometimes used to treat polycythemia vera (a blood disease in which your body makes too many red blood cells). Talk to your doctor about the risks of using this medication for your condition.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking hydroxyurea,

• Tell your doctor and pharmacist if you are allergic to hydroxyurea, any other medications, or any of the inactive ingredients in hydroxyurea capsules or tablets. Ask your pharmacist for a list of the ingredients.
• Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: certain medications for HIV (human immunodeficiency virus) such as didanosine (Videx) and stavudine (Zerit) and interferon (Actimmune, Avonex, Betaseron, Infergen, Intron A, others). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• Tell your doctor if you have human immunodeficiency virus (HIV), acquired immunodeficiency syndrome (AIDS), high levels of uric acid in your blood, or leg ulcers; if you are being treated with or have ever been treated with radiation therapy, cancer chemotherapy, or hemodialysis; or if you have or have ever had kidney or liver disease.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. You should not become pregnant or breastfeed while you are taking hydroxyurea. You will need to have a pregnancy test before you begin treatment with hydroxyurea. If you are a female, you should use effective birth control while taking hydroxyurea and for at least 6 months after stopping your treatment. If you are a male, you and your female partner should use effective birth control while taking hydroxyurea and for at least 6 months (Siklos) or at least 1 year (Droxia, Hydrea) after stopping your treatment. Talk to your doctor about birth control methods that you can use during and after your treatment and how long you should continue their use. If you become pregnant while taking hydroxyurea, call your doctor immediately. Hydroxyurea may harm the fetus.
• You should know that this medication may decrease fertility in men. Talk to your doctor about the risks of taking hydroxyurea.
• Do not have any vaccinations without talking to your doctor.

Unless your doctor tells you otherwise, continue your normal diet.

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Hydroxyurea may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Nausea
• Vomiting
• Diarrhea
• Loss of appetite
• Weight gain
• Sores in the mouth and throat
• Constipation
• Rash
• Pale skin
• Dizziness
• Headache
• Hair loss
• Changes in skin and nails

Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately or get emergency medical treatment:

• Fast heartbeat
• Ongoing pain that begins in the stomach area but may spread to the back
• Leg wounds or ulcers
• Pain, itching, redness, swelling, or blisters on the skin
• Pain in the upper right part of the stomach
• Blood in the urine
• Yellowing of the skin or eyes
• Numbness, burning, or tingling in the hands or feet
• Fever, cough, shortness of breath, and other breathing problems

Hydroxyurea may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children and pets. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Broken 1,000-mg tablets must be stored in the container and must be used within 3 months.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

• Sores in the mouth and throat
• Pain, redness, swelling, and scaling on the hands and feet
• Darkening of the skin

Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking hydroxyurea.

Do not let anyone else take your medication. People who are not taking hydroxyurea should avoid touching the medication or the bottle that contains the medication.

Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.