Hydroxyurea

At a Glance

What is Hydroxyurea?

Hydroxyurea is an oral cytotoxic medicine that acts on rapidly dividing cells. It is used to treat sickle cell disease and certain cancers, including leukemia. It is not a cure for either condition. The goals of treatment differ. In sickle cell disease the aim is fewer painful crises and complications, and in cancer it is control of the disease. It should be prescribed and monitored by a hematologist or oncologist, and the product and dose depend on the condition being treated.

How Hydroxyurea Works

• In sickle cell disease: Hydroxyurea increases fetal hemoglobin (HbF), a form of hemoglobin present in fetuses that helps prevent red blood cells from sickling. It also lowers neutrophils, makes sickled cells more flexible, and changes how red cells stick to blood vessel walls. The exact way it benefits sickle cell disease is not fully understood, and several effects probably contribute.
• In cancer: It inhibits DNA synthesis by blocking an enzyme called ribonucleotide reductase, which slows the growth of cancer cells.

When Hydroxyurea Is Used

• Sickle cell disease: Used to reduce the frequency of painful crises and the need for blood transfusions in people with recurrent moderate to severe painful crises. In a trial in adults, hydroxyurea reduced painful crises, acute chest syndrome episodes and transfusions compared with placebo.
• Cancer (US Hydrea-label indications): Resistant chronic myeloid leukemia (CML), and locally advanced squamous cell carcinoma of the head and neck (excluding the lip) together with chemoradiation.
• Polycythemia vera and similar blood disorders: Specialists may use hydroxyurea in some myeloproliferative neoplasms, such as polycythemia vera. This use is not necessarily an indication in the specific US Hydrea or Droxia labels, and labeling differs by country, so the decision belongs to the specialist.
• HIV (not approved): Hydroxyurea is not indicated for HIV. Combining it with certain HIV medicines can cause serious toxicity (see Drug Interactions).

Hydroxyurea Dosage and How to Take It

Doses depend on the condition, the product, age, kidney function and blood counts. Sickle cell and cancer doses are not interchangeable, and the examples below are product-specific, from US prescribing information. Your hematologist or oncologist decides the dose. Swallow capsules whole with water, and do not open, break or chew them.

Sickle cell disease

• Adults, Droxia capsules (Droxia-specific dosing): The starting dose is 15 mg/kg once daily, based on actual or ideal weight, whichever is less. The dose may be increased by 5 mg/kg/day every 12 weeks, only if blood counts are in an acceptable range, up to the maximum tolerated dose or 35 mg/kg/day. If blood counts become toxic, treatment is paused and resumed at a lower dose after recovery.
• Children (product-specific): Pediatric dosing depends on the product and must be directed by the child’s doctor. For example, the Siklos tablets label lists a starting dose of 20 mg/kg once daily for children 2 years and older (15 mg/kg for adults), with increases every 8 weeks. The Droxia label says safety and effectiveness in pediatric patients have not been established. Do not use 20 mg/kg/day as a general pediatric hydroxyurea dose.
• Kidney impairment (Droxia-specific): Droxia’s label reduces the dose by 50%, with a starting dose of 7.5 mg/kg, when creatinine clearance is below 60 mL/min. Other products may differ, so do not apply this reduction to other hydroxyurea products without checking their labels.

Cancer (Hydrea prescribing-information examples)

• Resistant CML: 20 to 30 mg/kg once daily.
• Head and neck cancer: 80 mg/kg once every third day, given with chemoradiation.
• Cancer dosing is individualized by the type and stage of cancer, other treatments, your response, blood counts and the oncologist’s plan. Treatment may be interrupted if blood counts fall too low.

The 35 mg/kg/day figure belongs to the sickle cell dosing context. It is not a general dose ceiling for cancer.

Take this medicine only as advised by your doctor or healthcare professional. Do not start, stop, or change the dose on your own.

Side Effects of Hydroxyurea

Common side effects include:

• Low white blood cells (usually the first sign of bone marrow suppression), and sometimes low platelets or anemia
• Nausea, vomiting, diarrhea, constipation, mouth sores and loss of appetite
• Hair loss, skin rash, darkening of the skin or nails, and larger-than-normal red blood cells (macrocytosis)
• Headache, dizziness and drowsiness

Serious side effects need prompt medical attention:

• Severe myelosuppression: fever, infections, unusual bruising or bleeding. This can occur even at the recommended starting dose.
• Secondary cancers: leukemia and skin cancer have been reported with long-term use.
• Skin ulcers and vasculitic ulcers (including gangrene), mainly reported in blood cancers, especially with a history of interferon
• Hemolytic anemia (jaundice or dark urine with worsening anemia)
• Lung problems: fever, cough or breathlessness (reported mainly in myeloproliferative disease)
• Liver problems: raised liver enzymes, cholestasis or hepatitis
• Radiation recall: hydroxyurea can cause or worsen a skin reaction (redness) in an area that previously received radiation. Tell your doctor if you have had radiation, and report any new redness or soreness in that area.
• Fertility effects: low or absent sperm counts (azoospermia, oligospermia) in men
• Drug-induced fever, and rarely severe allergic reactions

Hydroxyurea Precautions and Monitoring

Requirements can differ by product and indication, so follow your doctor’s instructions and your product’s information.

• Contraindication: People who have had a hypersensitivity reaction to hydroxyurea or its ingredients should not take it. Treatment should not be started if bone marrow function is markedly depressed.
• Blood count monitoring: The exact frequency depends on the product, condition, dose and clinical situation. For example, the Droxia sickle cell label advises blood counts every 2 weeks, and the US hydroxyurea capsule labeling for cancer advises at least weekly counts. Follow the schedule your doctor sets. Siklos and other products have their own schedules.
• Kidney and liver tests: May be needed, particularly if you have kidney or liver problems.
• Vaccines: Avoid live vaccines, because they can cause severe infection.
• Sun protection: Use sunscreen and protective clothing, and have your skin checked for new or changing lesions.
• Folic acid: The Droxia label recommends folic acid, because hydroxyurea can mask folic acid deficiency.
• Handling: Hydroxyurea is a cytotoxic drug. Caregivers may need to wear disposable gloves when handling capsules or bottles, and wash their hands with soap and water before and after. Avoid contact with opened or crushed capsules.
• Lab results: It can falsely raise some uric acid, urea and lactic acid test results.
• Sperm preservation: Men may be advised about sperm banking before treatment.

Hydroxyurea Drug Interactions

• Antiretroviral (HIV) medicines: Pancreatitis, liver toxicity (including fatal cases) and nerve damage have occurred when hydroxyurea was given with certain HIV medicines, including didanosine and stavudine. The combination of hydroxyurea, didanosine and stavudine should be avoided, and anyone with HIV on these medicines needs close monitoring.
• Other myelosuppressive medicines: Medicines that also lower blood counts can add to the effect on bone marrow, so your doctor may need to monitor you more closely. Bone marrow suppression is more likely in people who have previously had radiotherapy or chemotherapy.
• Radiation therapy: Hydroxyurea is often combined with radiation in head and neck cancer under specialist supervision. It can cause radiation recall in previously irradiated skin (see Side Effects).
• Live vaccines: Avoid, as described above.

Tell your doctor and pharmacist about all prescription medicines, over-the-counter medicines and supplements you take. This list is not complete.

Hydroxyurea in Pregnancy and Breastfeeding

• Pregnancy: Hydroxyurea can cause fetal harm. Pregnancy should be ruled out before starting treatment. The recommendations below are product-label recommendations (from the Droxia label for sickle cell disease, and the US hydroxyurea capsule label for cancer on the female timeline), not necessarily universal rules, so check your product’s information.
  • Females of reproductive potential: use effective contraception during treatment and for at least 6 months afterwards.
  • Males with female partners of reproductive potential (Droxia label): use effective contraception during treatment and for at least 1 year afterwards.
  • Contact your doctor immediately if you become pregnant, or if your partner does.
• Breastfeeding: Hydroxyurea passes into breast milk, and the relevant labeling advises discontinuing breastfeeding during treatment because of the risk of serious adverse reactions in the infant, including carcinogenicity. Discuss breastfeeding and treatment decisions with your doctor.

Hydroxyurea Brands, Strengths and Approximate Price in India

Examples of hydroxyurea brands marketed in India may include Hydrea, Cytodrox and Durea, based on online pharmacy listings. This is time-sensitive, not exhaustive, and availability can change. Droxia is a US brand name, and I could not confirm that it is sold in India.

• Strengths: Indian listings most commonly show 500 mg capsules. Other strengths may exist for sickle cell dosing, so check the exact strength with your doctor or pharmacist.
• Approximate price in India (listing-based): Online pharmacy listings show roughly ₹5–₹12 per 500 mg capsule (about ₹50–₹120 per strip of 10). These may be selling prices rather than MRPs and can differ between sources, so this is not a guaranteed current MRP or the price of hydroxyurea in general.

Prices may vary by brand, strength, pack size, pharmacy and location.

How HealthPil Can Help

Medicines should be started, adjusted, or stopped only under the guidance of a qualified healthcare professional. If you have questions about this medicine, its side effects, or your treatment plan, you can consult a doctor through HealthPil, including hematologists and oncologists for sickle cell disease and cancer treatment.