# Hydroxyurea (hydroxycarbamide)

Source: https://onco.cc/drugs/hydroxyurea/  
OnCo record `hydroxyurea` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Hydroxyurea is a cheap, decades-old pill that lowers high blood counts in polycythaemia vera and essential thrombocythaemia and is also the main drug for sickle cell disease.

## Summary

First-line cytoreduction in high-risk PV and ET (reduces thrombosis; PT-1 trial superior to anagrelide in ET). Historic role in CML before imatinib. Also used in sickle cell disease and, less often, for leukocytosis in acute leukaemia. Concerns: leg ulcers, skin cancers, questionable leukaemogenicity.

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-08
- Tags: gap-fill; generic
- Brand: Hydrea / Droxia / Siklos
- Modality: Oral ribonucleotide reductase inhibitor (cytoreductive)
- Mechanism: Inhibits ribonucleotide reductase, depleting deoxyribonucleotides and arresting S-phase; lowers blood counts in myeloproliferative disease.
- Approvals: US 1967: CML, head and neck cancer with radiotherapy, melanoma, ovarian cancer (historic labelling); US 1998: Sickle cell anaemia (Droxia)

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Hydroxycarbamide
- Label (DailyMed): https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=hydroxyurea

## Connected records

- cancers: [Acute myeloid leukaemia in older or unfit patients](https://onco.cc/cancers/aml-older-unfit/), [Chronic myeloid leukaemia (CML)](https://onco.cc/cancers/cml/), [Chronic myelomonocytic leukaemia and MDS/MPN overlap neoplasms](https://onco.cc/cancers/cmml/), [Essential thrombocythaemia (ET)](https://onco.cc/cancers/essential-thrombocythaemia/), [Myeloproliferative neoplasms (PV, ET, myelofibrosis)](https://onco.cc/cancers/myeloproliferative-neoplasms/), [Polycythaemia vera (PV)](https://onco.cc/cancers/polycythaemia-vera/), [Primary myelofibrosis](https://onco.cc/cancers/primary-myelofibrosis/)
- technologies: [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/)
- companies: [Bristol Myers Squibb](https://onco.cc/companies/bms/)
- targets: [Ribonucleotide reductase (RRM1)](https://onco.cc/targets/rrm1/)
- drugs: [Anagrelide](https://onco.cc/drugs/anagrelide/), [Mitobronitol](https://onco.cc/drugs/mitobronitol/), [Phosphorus-32 (radiophosphorus)](https://onco.cc/drugs/phosphorus-32/), [Pipobroman](https://onco.cc/drugs/pipobroman/)
- trials: [A Study of Low Dose Interferon Alpha Versus Hydroxyurea in Treatment of Chronic Myeloid Neoplasms](https://onco.cc/trials/nct01387763/), [CYTO-PV](https://onco.cc/trials/cyto-pv/), [PROUD-PV and CONTINUATION-PV](https://onco.cc/trials/proud-pv/), [PT-1 (Primary Thrombocythaemia 1)](https://onco.cc/trials/pt-1/)
- terms: [IPSET-thrombosis score (essential thrombocythaemia)](https://onco.cc/terms/ipset-thrombosis/), [MPN driver mutations (JAK2 V617F, CALR, MPL) and allele burden](https://onco.cc/terms/mpn-driver-mutations/)
- pathways: [DNA replication & origin licensing](https://onco.cc/pathways/dna-replication-licensing/)

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