Author: Dr Amanda Oakley, Dermatologist, Waikato Hospital, Hamilton, New Zealand, 2001.

Hydroxyurea (trade name in New Zealand "Hydrea") is a cytotoxic agent. It is also known as hydroxycarbamide. It is sometimes used to treat plaque psoriasis, usually at a dose of 500 mg to 1 g orally daily. It is less effective for pustular psoriasis, guttate psoriasis or psoriatic arthritis.

Hydroxyurea is more frequently prescribed for patients with chronic myeloid leukaemia, cervical cancer and a variety of other malignancies and myeloproliferative disorders. It is also used in sickle cell disease and in HIV infection.

Mechanism of action

Hydroxyurea is converted to a free radical nitroxide. In psoriasis, it is thought to work by reducing the replication of DNA within the basal cell of the epidermis. A response is noted in about half of treated patients, sometimes in those resistant to other therapies such as methotrexate, acitretin or phototherapy. Improvement usually begins about two weeks after starting treatment, and is maximum after about eight weeks.

In resistant cases, hydroxyurea can be cautiously combined with other antipsoriatic drugs. Care should be taken if combined with methotrexate as both drugs may suppress bone marrow function increasing toxicity.

Hydroxyurea should not be taken in pregnancy as it is likely to cause fetal abnormalities. It should not be taken by a breast feeding mother. Its safety in children is unknown.

Side effects

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.

Related information

Email Newsletter

Would you like to receive our dermatology updates by email?


Submit your images

We're seeking high-quality photos of skin diseases.  


Machine diagnosis

Watch DermNet's proposal to create a 'Skin Disease Image Recognition Tool' - winner of the 2017 'Clinicians' Challenge Active Award' by the NZ Ministry of Health and HiNZ.

Subscribe to our mailing list

* indicates required
DermNet NZ Newsletter