Hydroxyurea (Hydrea)

Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.

About Hydroxyurea

What it is

Hydroxyurea (hydroxycarbamide) blocks ribonucleotide reductase, slowing DNA production in fast-dividing cells. In sickle cell disease it raises the level of fetal haemoglobin, which stops red cells from sickling, and reduces pain crises; it is also used for some blood cancers such as polycythaemia vera and chronic myeloid leukaemia. It is sold as Hydrea, Droxia and Siklos, among other names.

How genes come into it

Most gene studies on hydroxyurea come from sickle cell disease and looked at genes that control fetal haemoglobin, such as BCL11A and the HBG2 region (including the XmnI variant), and at MAP3K5 and others, for how much fetal haemoglobin rose. The findings come from a few studies, and there is no CPIC or DPWG guideline. The sickle cell condition itself is caused by the HBB gene and is not something this medicine changes.

What research found

Every published finding on gene variants and Hydroxyurea. Upload your DNA file to see which of these rows apply to you.

Rated evidence (2 rated variants)

PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.

MAP3K5 rs9376230: Level 3. Efficacy: Beta-thalassemia and related diseases. 1.

MAP3K5 rs9483947: Level 3. Efficacy: Beta-thalassemia and related diseases. 1.

Response (21 findings)

Studies of how well it worked in people carrying a variant.

ASS1 rs10793902: Allele T is associated with increased response to hydroxyurea in people with Anemia, Sickle Cell and beta-Thalassemia as compared to allele C.

ASS1 rs10901080: Allele T is associated with increased response to hydroxyurea in people with Anemia, Sickle Cell and beta-Thalassemia as compared to allele G.

BCL11A rs1427407: Allele T is associated with increased response to hydroxyurea in people with beta-Thalassemia as compared to allele G.

BCL11A rs4671393: Allele A is associated with increased response to hydroxyurea in people with beta-Thalassemia as compared to allele G.

Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.

Related Drugs

More drugs from the same category

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Alimta (Antimetabolites)

Cytosar-U (Antimetabolites)

Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.

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Content updated September 2026.

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