Hydroxyurea in sickle cell anaemia

Hydroxyurea, also known as hydroxycarbamide could be used to treat both children and adults with moderate to severe disease (1). It promotes

• fetal haemoglobin (HbF) synthesis
• improves red cell hydration
• decreases neutrophil count
• modifies red cell-endothelial cell interactions
• acts as a nitric oxide donor (1)

Randomised controlled trials have shown that hydroxyurea helps in reducing the number of painful episodes, incidence of chest syndrome and the necessity of transfusion. Long term follow up studies have shown that survival at 10 years has also improved in patients taking the drug (2)

Indications for hydroxyurea use include:

• patients who have had 3 or more painful crises per year over the past 2 years requiring hospital admission
• or have recurrent crises in the community which are severe enough to interfere with their activities of daily living
• or who have had 2 or more acute chest syndromes (2)

Before starting treatment, patients should be given written information about the drug and the side effects should be discussed. A blood count should be done 2 weeks after initiating therapy and also after each dose increase. Liver function test and urea and electrolytes test should be carried out every 8 weeks (2).

Side effects of hydroxyurea include:

• myelosuppression - most common short term side effect of therapy (1)
• other side effects include hyperpigmentation of nails, nausea and vomiting, skin rash, alopecia and diarrhoea (2)
• an increased incidence of leukemia has been reported in patients who already have conditions which predisposes to leukemia e.g. polycythaemia rubra vera (1).

Women on treatment should use contraception due to the risk of teratogenecity. If a woman wishes to become pregnant or a man wishes to father a child, treatment should be stopped 3 months before conceiving. If a woman becomes pregnant during therapy, hydroxyurea should be discontinued immediately and should be commenced after breast feeding has stopped (2).

Reference:

• 1. NHS Sickle Cell and Thalassaemia Screening Programme 2009. Sickle cell and Thalssaemia. Handbook for laboratories
• 2. Sickle Cell Society 2008. Standards for the clinical care of adults with sickle cell disease in the UK