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Hydroxyurea capsules

Droxia, Hydrea, Siklos

You will be prescribed hydroxyurea by a specialist physician.

Please keep your regular clinic appointments so that your physician can check on your progress. You will need to have regular blood tests.

If you think you are getting an infection or if you have a high temperature (fever), please contact your physician for advice straightaway.

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About hydroxyurea

Type of medicine

A cytotoxic medicine (antimetabolite)

Used for

Some cancers; polycythemia rubra vera; sickle cell disease

Also called

Droxia®; Hydrea®; Siklos®

Available as


Hydroxyurea (also known as hydroxycarbamide) is prescribed for a number of different conditions. There are three brands of the medicine available. The brand of hydroxyurea capsules called Hydrea® is prescribed for people with some types of cancer, and also for people with a condition known as polycythemia rubra vera. The brands of hydroxyurea capsules called Droxia® and Siklos® are prescribed for people with sickle cell disease. It is important that each time you collect a new supply of medicine, you make sure it is the same brand of hydroxyurea that you have had before.

The types of cancer which can be treated with Hydrea® capsules include chronic myeloid leukaemia (CML) and cancers of the head and neck. In cancer, certain cells in the body grow and multiply too quickly. Anti-cancer medicines like hydroxyurea work by interfering with the growth of the cancer cells.

Polycythemia rubra vera is a disorder where the bone marrow makes too many blood cells. This leads to an abnormally high number of red blood cells being in your blood, making it 'thicker' than normal. Hydrea® capsules work by slowing down the production of the red blood cells.

Droxia® and Siklos® capsules are prescribed to ease painful conditions associated with sickle cell disease. In this condition, red blood cells have a tendency to go out of shape and can then block blood vessels, causing pain. Hydroxyurea can help to reduce these episodes of pain by helping to prevent the blood cells from going out of shape.

Before taking hydroxyurea

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking hydroxyurea it is important that your physician knows:

  • If you are pregnant or breastfeeding.

  • If you have any problems with the way your liver or kidneys work.

  • If you have had irradiation therapy in the past.

  • If you have any leg ulcers.

  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take hydroxyurea capsules

  • Before you start the treatment, read any printed information you have been given by your physician and the printed manufacturer's leaflet from inside the pack. These will give you more information about hydroxyurea and will provide you with a full list of the side-effects which you may experience from taking it.

  • Hydroxyurea will be given to you by a specialist physician who is experienced in treating your condition. Your physician will calculate what dose is right for you, and will tell you how much to take and how often to take it. You may be asked to take a dose each day, or every third day. Your dose will be printed on the label of the pack to remind you about what the physician said to you, but if you have any concerns, contact your physician or hospital clinic for advice.

  • Swallow the capsules whole with a drink of water. You can take hydroxyurea capsules either with or without food, but taking your dose with a meal may reduce feelings of nausea.

  • You should not open Hydrea® or Droxia® capsules as the powder inside can irritate your skin. When handling the capsules, take care to avoid prolonged skin contact and wash your hands after handling the bottle and capsules.

  • If you forget to take a dose, take it as soon as you remember unless it is nearly time for your next dose, in which case miss out the forgotten dose. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

  • You must try to keep your regular appointments with your physician or hospital. This is so your physician can check on your progress. You will need to have regular blood tests and check-ups during your treatment with hydroxyurea. The blood tests are important as a way of monitoring your treatment, and also to check that your kidneys and liver are working properly.

  • Your physician may also prescribe a vitamin tablet called folic acid. Taking this vitamin can help reduce the severity of some side-effects associated with hydroxyurea.

  • It is important that you do not get pregnant while you are taking hydroxyurea. Make sure you have discussed with your physician which types of contraception are suitable for you and your partner. Many anti-cancer treatments are associated with reduced fertility (particularly in men), so you may also want to ask your physician for family planning advice if you would like to have children.

  • While you are taking hydroxyurea and for six months after you have stopped the treatment, do not have any immunisations (vaccinations) without talking to your specialist physician first. Hydroxyurea lowers your body's resistance and there is a risk that you will get an infection from some vaccines.

  • Rarely, people who take hydroxyurea over a long period of time can develop skin cancer. You can reduce the risk of this by protecting your skin from the sun by wearing suitable clothing and using a sunscreen with a high sun protection factor (SPF) of at least 15.

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Can hydroxyurea cause problems?

Medicines like hydroxyurea which can be used to treat cancer can have a number of side-effects, some of which you might not experience until several days or weeks after starting the medicine. They can lower the number of white cells in your blood, which increases the risk of you getting an infection. While you are taking hydroxyurea you should take precautions to reduce the risk of getting an infection - you can do this by avoiding being with people who you know have an infection. If you think you are getting a sore throat or if you have a high temperature (fever), please let your physician know as soon as possible so that you can get some treatment straightaway.

Your physician will discuss with you the possibility of unwanted side-effects from your treatment. The table below contains some of the most common side-effects associated with hydroxyurea, although not everyone experiences these. You will find a full list in the manufacturer's information leaflet supplied with your treatment. Please let your physician know if you experience any of the following:

Very common hydroxyurea side-effects (these affect more than 1 in 10 people)

What can I do if I experience this?

Decreased number of white or red blood cells, or platelets

Let your physician know if you are getting a sore throat or if you have a high temperature. If you notice any unusual bleeding or bruising, contact your physician straightaway

Nausea, loss of appetite, diarrhea or constipation, tummy (abdominal) pain, indigestion

Stick to simple meals. If troublesome, let your physician know

Sore mouth

Ask your physician for advice on a suitable remedy

Skin reactions and nail disorders

Ask your physician for advice

Headache, chills, high temperature

Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the headaches continue, speak with your physician

If you experience any other symptoms which you think may be due to this medicine, speak with your physician or pharmacist.

How to store hydroxyurea

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the emergency room of your local hospital. Take the container with you, even if it is empty.

If you buy any medicines check with a pharmacist that they are safe to take with your prescribed medicines.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Ask your pharmacist about ways to dispose of medicines safely in your local area.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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