Hydroxyurea for Sickle Cell Disease

What is hydroxyurea?

Hydroxyurea is a chemotherapy medicine that has been used to treat many disorders, including sickle cell disease. Research has shown that patients with sickle cell disease who take hydroxyurea:

• are admitted to hospital because of painful events only half as often as patients who do not take hydroxyurea
• have fewer episodes of acute chest syndrome
• have less need for blood transfusions if they are admitted to hospital

You may hear hydroxyurea called by its brand name, Hydrea. Hydroxyurea comes in a capsule form.

Your child may be offered hydroxyurea if

• they have had three or more admissions to the hospital for significant painful episodes in the last 12 months
• they have needed one or more exchange transfusions for one or more episodes of acute chest syndrome
  
• they have taken significant time away from school or work due to painful episodes managed at home

Before hydroxyurea is given to your child

Tell your child's doctor if your child has had an allergic reaction to hydroxyurea or a component of its formulation or if your child has any immune or blood disorder (besides sickle cell disease).

Talk with your child's doctor or pharmacist if your child has any of the following conditions. Precautions may need to be taken with these medicines if your child:

• has liver disease
  
• has kidney disease
• may be pregnant
  

How is hydroxyurea given to your child?

• Give your child hydroxyurea exactly as your doctor or your pharmacist tells you to. Talk to your child's doctor before you stop giving this medicine for any reason. It may take a few months until its full effect is seen.
• Blood testing may be done every two months when starting this medication to find the right dose for your child.
• Give your child hydroxyurea once a day, around the same time every day. Many patients prefer to take it at bedtime.
• You may give hydroxyurea with or without food. Giving it with food may help to prevent stomach upset.
• Your child should drink lots of fluids (liquids) each day.
• If your child throws up (vomits) less than half an hour after taking hydroxyurea, give another dose of the medicine. If your child vomits more than half an hour after taking hydroxyurea, do not give another dose. Give the next dose the next day at the usual time.
• Hydroxyurea is supplied as a 500 mg capsule in Canada. Your child should swallow the capsule whole with a glass of water or other liquid.
• If your child is not able to swallow capsules or is taking a dose that is less than a whole capsule, review the best way to give hydroxyurea with the pharmacist. The capsule can be opened and dissolved in a medication syringe to give the prescribed dose. Throw away the left-over medicine.
• The pharmacist will teach you how to handle hydroxyurea safely, including using gloves when mixing powder from the capsule. The pharmacist will also teach you how to throw away the medicine safely.
• Anyone handling hydroxyurea should wash their hands before and after touching the bottle or capsules. For more detailed instructions on safely handling and storing hydroxyurea, see Chemotherapy at home: Safely giving your child capsules.
  

What should you do if your child misses a dose of hydroxyurea?

• If a dose is missed, do not give a make-up dose.

How long does it take hydroxyurea take to work?

It could take a few months before changes are seen in blood work.

What are the possible side effects of hydroxyurea and how are they monitored?

Your child may have some of these side effects while they take hydroxyurea. Check with your child's doctor if your child continues to have any of these side effects and they do not go away, or they bother your child:

• Nausea and vomiting: Avoid taking hydroxyurea on an empty stomach.
• Skin rash: This may be a non-specific rash that goes away even when the medication is continued. If a rash develops, see the doctor who prescribed hydroxyurea to your child.
• Hair loss: There can be thinning of the hair. The hair loss does not usually result in bald spots. If this happens, the risk and benefit of taking hydroxyurea (improved health and fewer episodes) must be discussed with your child's doctor to decide about continued use of the drug.
• Lowering of some blood counts: Your child needs to have a blood test to check blood counts every two months for the first year of treatment. These tests can be done at a local laboratory and the results are sent to your child's doctor. If the counts are below a predetermined acceptable level, you will be called to hold the drug and repeat the blood test in seven days. The counts usually recover and the drug can be continued as prescribed. If the white cell count falls again, then the dose will be reduced to the dose your child was on before the counts started to fall. Your child will keep taking this lower dose.
• Skin and nail darkening: After taking hydroxyurea for some time, some patients develop darkening of the nails and skin over creases such as knuckles. This effect goes away once the drug is no longer in use.
• Liver dysfunction (problems): This is unusual, but blood tests are taken every three months to assess for this complication.
• Headache.
  
• Muscle weakness, mostly in the thighs and upper arms.
• Mouth irritation or sores: Using a soft toothbrush and rinsing the mouth may help.
• Long-term effects: Hydroxyurea is a chemotherapy drug, and some of these types of drugs have been associated with patients developing cancer over many years. But in over 20 years of hydroxyurea use in sickle cell disease patients, there have been no reported cases of this medicine causing cancer.

What safety measures should be taken when your child is using hydroxyurea?

Hydroxyurea can temporarily lower your child's blood counts, which makes them more likely to get an infection. To prevent infections, your child should avoid people with infections, such as a cold or the flu, especially when their blood count is low.

There is a chance that hydroxyurea may cause birth defects if it is taken at the time of conception or if it is taken during pregnancy. If you are a young woman who is sexually active, you should use some kind of birth control while receiving hydroxyurea. If you get pregnant while taking hydroxyurea, you should stop taking it right away and let your doctor know.

You should stop taking hydroxyurea for at least three months before trying to get pregnant. Hydroxyurea may also lower sperm counts.

If your child has HIV and is taking medicine for this condition, particularly didanosine and/or stavudine, talk with your child's doctor.

This is not a complete list. Check with your child's doctor or pharmacist before giving your child any other medicines (prescription, non-prescription, herbal, or natural products).

As a parent or caregiver, the risk of harm from handling hazardous medicine is small, however, it is a good idea to minimize or avoid exposure. This includes not tasting your child’s medication. Also, if you are pregnant or breastfeeding, it is best to avoid contact with hazardous medicine. If possible, have someone else give your child their medication.

Hazardous medicine can damage healthy cells. Anyone handling hazardous medicine should keep themselves protected. You may want to consider wearing gloves and a mask when handling your child’s medication. Also, before preparing your child’s medication wash your hands with soap and water.

What other important information should you know about hydroxyurea?

• The drug has to be taken every day, not just when a painful episode starts. It will not take away the pain in an active episode. It works by making changes to the blood cells which prevent episodes. It reduces sickling, decreases red cell breakdown, and increases protective fetal hemoglobin.
• At the one-month visit, the red blood cells are larger. This is seen on testing and looking under the microscope. These red cells are able to move through the tiny blood vessels more easily and break less easily. Parents often report that their child's appetite has increased.
• By three months on the drug, there is also an increase in the fetal hemoglobin and overall hemoglobin level. We know that patients with higher fetal hemoglobin levels have fewer episodes.
• By six months, your child should have had fewer painful episodes than in the six months before starting treatment.
• How long a patient continues to take the drug will be a decision between them and the treating physician.
• Hydroxyurea is covered by all private insurance plans and Ontario Drug Benefit plan.
• Do not share your child's medicine with others. Do not give anyone else's medicine to your child.
• Make sure you always have enough hydroxyurea to last through weekends, holidays, and vacations. Call your pharmacy at least two days before your child runs out of medicine to order refills.
• Keep hydroxyurea at room temperature in a cool, dry place away from sunlight. Do NOT store it in the bathroom or kitchen.
• Do not keep any medicines that are out of date. Check with your pharmacist about the best way to throw away outdated or leftover medicines.

Keep hydroxyurea out of your child’s sight and reach and locked up in a safe place. If your child takes too much hydroxyurea, call your local Poison Information Centre at one of these numbers. These calls are free. 

• Call 1-844 POISON-X, or 1-844-764-7669, from anywhere in Canada except Quebec.
• Call 1-800-463-5060 if you live in Quebec.