Hydroxycarbamide (Hydroxyurea)

How it works

It inhibits ribonucleotide reductase, depleting the deoxyribonucleotide pool required for DNA synthesis and thereby suppressing rapidly dividing cells; in sickle cell disease it also raises foetal haemoglobin, which reduces sickling.

Prescribing in practice

• Myelosuppression is dose-limiting and can be profound, so the full blood count must be checked before and regularly during treatment, with dose interruption for cytopenias.
• It is teratogenic and genotoxic; effective contraception is required for both sexes and pregnancy and breastfeeding should be avoided.
• Cutaneous reactions including leg ulcers and an increased risk of secondary malignancy with long-term use warrant ongoing skin and clinical surveillance.

Monitoring

Monitor the full blood count regularly throughout treatment, with periodic renal and hepatic function, and review the skin for ulceration.

Counselling the patient

• Handle the capsules with care, avoid opening them, and wash hands after handling.
• Report fever, sore throat, unusual bruising or bleeding, or any new leg ulcer promptly.
• Use reliable contraception and discuss any pregnancy plans with the team before stopping.

Evidence & guidelines

Cytoreduction with hydroxycarbamide for high-risk myeloproliferative neoplasms and its role in reducing sickle cell crises are well established in haematology guidance.