Hydroxycarbamide treatment in adults with sickle cell disease (SCD) Information for patients, relatives and carers

This information has been provided to answer some of the questions you may have about treatment with hydroxycarbamide (also known as hydroxyurea) in sickle cell disease.

Together with advice from your specialist team this will help you to make an informed decision about starting hydroxycarbamide.

What is hydroxycarbamide?

Hydroxycarbamide is a drug that has been used for many years to treat blood disorders and certain types of cancer. It has also been found to be beneficial in sickle cell disease (SCD).
Findings from a research study conducted in the USA in the 1990s first showed that many sickle cell patients taking hydroxycarbamide experienced fewer pain crises and episodes of acute chest syndrome and require fewer blood transfusions. More recent evidence shows that hydroxycarbamide can also improve life expectancy in SCD.
Hydroxycarbamide is usually recommended if you have had three or more hospital admissions in the past year for a sickle cell crisis, have regular crises at home affecting work or normal daily life or have had two or more episodes of acute chest syndrome during your lifetime. There may be other reasons why hydroxycarabamide could benefit you and this will be discussed with you by your haematology team.

How does hydroxycarbamide work in SCD?

Hydroxycarbamide works in several ways by:

1. Increasing the number of red blood cells containing fetal haemoglobin (HbF). Having more HbF is a good thing in SCD. During the first few months of life red blood cells contain mostly HbF and in SCD this protects against sickling. As the level of HbF falls the benefit wears off. Some people with SCD naturally produce more HbF throughout life. They have fewer problems and live longer. Hydroxycarbamide stimulates production of HbF – this effect may take a few months.

2. Helping to keep red cells well-hydrated and reducing their stickiness. This may prevent a sickle crisis developing. These effects occur quite quickly which may explain why some people feel better and experience less pain within a few weeks of starting treatment.

3. Reducing the number of white blood cells which is often high in people severely affected by SCD. These cells produce chemicals that can cause inflammation and trigger a crisis. Having fewer white cells makes sickling less likely.

How do I take hydroxycarbamide?

Hydroxycarbamide comes in 500 mg capsules and is taken by mouth once a day. It is usually started at a low dose which is gradually increased according to the tolerability and so that it produces the desired effect. This will be monitored and adjusted when you attend the outpatient clinic. The maximum dose depends on your weight, blood counts and how you respond to the drug but for adults is usually three to four capsules per day.

Hydroxycarbamide should be taken either before or after food at approximately the same time each day. The capsules should be swallowed whole with plenty of water. Take care not to break open the capsules – if this happens accidentally, wash your hands straight away. If you have difficulty swallowing the capsules, ask your doctor or pharmacist if hydroxycarbamide can be provided in a different form.

It is important to take hydroxycarbamide as prescribed to ensure you get the most benefit from treatment and avoid unwanted effects. If you miss a dose, take the next dose as usual and do not double it. If you experience side-effects or have been unable to take hydroxycarbamide regularly, it is important that you tell your doctor or clinical nurse specialist (CNS) as soon as possible. If you think you may run out of capsules before your next clinic appointment contact your clinical nurse specialist who will be able to arrange a prescription. If you take too much hydroxycarbamide by mistake, you should contact the haematology team urgently for advice.

Before you start treatment, please read the medication leaflet provided by pharmacy.

How do I store and dispose of hydroxycarbamide?

• Store in a dry place at room temperature
• Make sure it is placed in a secure location out of the reach of children and pets
• Return any unused medication to your hospital or local pharmacy
• Do not throw the capsules in the bin or flush them down the toilet

Are there any side effects associated with hydroxycarbamide?

Most people tolerate hydroxycarbamide treatment well but like all medicines there are some potential side effects. The risk of side-effects is reduced by reviewing you regularly in the clinic and monitoring your blood tests. Most side-effects are reversible on stopping or reducing the medication.

Low blood counts are a possible side-effect you should be aware of. If this happens you may:

• feel more tired or short of breath due to a fall in haemoglobin
• bruise or bleed more easily due to low platelets (a type of blood cell important in blood clotting)
• develop mouth ulcers or pick up infections more easily due to low white blood cells

If you experience any of the symptoms listed above or develop a fever greater than 38oC (100.4oF) you should contact the haematology emergency number (24/7) or go to the nearest A&E immediately.

You may not initially be aware if your blood counts are low so it is important to attend your clinic appointments for these to be checked. You can discuss any other symptoms that you are concerned about with your doctor or CNS at these appointments.

Other unwanted effects that can occur include an upset stomach (diarrhoea, constipation or nausea / vomiting), poor appetite, headaches or dizziness, allergic reaction such as skin rash, skin and nail pigmentation, hair thinning, skin ulceration, abnormal liver or kidney function tests. Most of these are uncommon.

There have been concerns that hydroxycarbamide may increase the risk of developing leukaemia and other cancers. However, after more than 20 years’ experience of its use in SCD in the UK and internationally, there is no evidence to support and increase in risk above the general population.

It is strongly advised that adequate contraceptive precautions should be taken to avoid becoming pregnant (or if you are male your partner becoming pregnant) whilst you are taking hydroxycarbamide. This is because of the possibility that the drug may have harmful effects on the developing baby (see below). You or your partner should use condoms even if another form of contraception is used. This also protects you or your partner from exposure to the small amounts of the drug present in semen or vaginal secretions and any possible harm that might result.

Can I take other medicines with hydroxycarbamide?

It is safe to take hydroxycarbamide with most other medications. You should let your doctor, CNS or pharmacists know about all other medications you are taking or are prescribed.

Live vaccines (e.g. yellow fever vaccine, shingles vaccine) should be avoided if you are taking hydroxycarbamide.

Can I eat and drink as usual?

Yes. Eat a balanced, healthy diet and drink plenty of water.

Can I drink alcohol while taking hydroxycarbamide?

Yes. You should not exceed the maximum recommended weekly limits of 21 units of alcohol for a man and 14 units for a woman.

What if I or my partner would like to become pregnant?

Hydroxycarbamide treatment does not stop you or your partner from having children. If you are planning to have children you should discuss this first with your haematologist or CNS. Hydroxycarbamide must be stopped for at least three months before conception to avoid any risk to the baby. While you are on treatment it is important to use reliable contraception.
If you or your partner becomes pregnant while taking hydroxycarbamide contact your doctor or CNS immediately for further advice.

There is no evidence that taking hydroxycarbamide reduces fertility although in men the sperm count may be reduced while taking the drug. This usually reverses on stopping treatment. As a precaution we advise you to consider sperm analysis and storage before starting treatment.


Can I breastfeed while taking hydroxycarbamide?

You should avoid hydroxycarbamide while breastfeeding because it is secreted in breast milk and could affect your baby.

Do I need to take any other special precautions?

Your skin may become more sensitive to the sun so please remember to protect it by using sunscreen.


Before you start treatment with hydroxycarbamide your doctor or CNS will seek your consent and may ask you to sign a consent form to confirm that you have understood the benefits and risks.

Contact details for advice/further information Imperial NHS


Please follow the video links for further information

Hydroxyurea - link

Hydroxyurea’s role in managing sickle cell disease - link

Effectiveness of hydroxycarbamide in pediatric SCD in the real world - link

Hydroxyurea is effective in treating sickle cell anemia in African children - link

SCDAAMI questions about Hydroxyurea - link

Sickle cell patients and Hydroxyurea treatment - link