Hydroxyurea: uses, dosing, side effects & brands
Hydroxyurea is a medicine sold in the U.S. under 4 brand and generic names, for brain neoplasms, non-small-cell lung carcinoma and renal cell carcinoma. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Treats (across its forms)
- Brain Neoplasms, Non-Small-Cell Lung Carcinoma and Renal Cell Carcinoma
- Available as
- Capsule · Tablet · Solution
- Sold as
- 4 products — Droxia, Hydrea and Siklos, and others
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
- Half-life
- about 2 to 4 hours
- What the pharmacy pays
- about $6 for a 30-count supply — not your price
- Boxed warning
- Boxed warning
How Droxia is dosed
From the FDA label for Droxia (application NDA016295). Other hydroxyurea products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Initial dose: 15 mg/kg once daily. Monitor the patient's blood count every two weeks. ( 2.1 ) The dose may be increased by 5 mg/kg/day every 12 weeks until a maximum tolerated dose or 35 mg/kg/day is reached if blood counts are in an acceptable range. ( 2.1 ) The dose is not increased if blood counts are between the acceptable range and toxic. Discontinue DROXIA until hematologic recovery if blood counts are considered toxic. Treatment may then be resumed after reducing the dose by 2.5 mg/kg/day from the dose associated with hematological toxicity. ( 2.1 ) Renal impairment: Reduce the dose of DROXIA by 50% in patients with creatinine clearance less than 60 mL/min. ( 2.2 , 8.6 , 12.3 ) 2.1 Dosing Information Table 1: Dosing Recommendation Based on Blood Count Dosing Regimen Dose Dose Modification Criteria Monitoring Parameters Initial Recommended Dosing 15 mg/kg/day as a single dose once daily based on the patient's actual or ideal weight, whichever is less. Monitor the patient's blood count every 2 weeks [see Warnings and Precautions (5.1) ] . Dosing Based on Blood Counts In an acceptable range Increase dose 5 mg/kg/day every 12 weeks Maximal dose: 35 mg/kg/day Maximal dose is the highest dose that does not produce toxic blood counts over 24 consecutive weeks. Increase dosing only if blood counts are in an acceptable range. Do not increase if myelosuppression occurs. Blood…
Everything below is the FDA label for Droxia (capsule). Hydroxyurea is also sold as tablet and solution, and those are different medicines to take — follow the label for the one you were prescribed.
Droxia side effects
The following clinically significant adverse reactions are described in detail in other labeling sections: Myelosuppression [see Warnings and Precautions (5.1) ] Hemolytic anemia [see Warnings and Precautions (5.2) ] Malignancies [see Warnings and Precautions (5.3) ] Vasculitic toxicities [see Warnings and Precautions (5.5) ] Risks with concomitant use of antiretroviral drugs [see Warnings and Precautions (5.7) ] Macrocytosis [see Warnings and Precautions (5.8) ] Pulmonary Toxicity [see Warnings and Precautions (5.9) ] Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Most common adverse reactions (≥30%) are hematological, gastrointestinal symptoms, and anorexia. (6) To report SUSPECTED ADVERSE REACTIONS, contact Waylis Therapeutics LLC at 1-844-200-7910 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trial Experience In 299 patients treated for sickle cell anemia in the Multicenter Study of Hydroxyurea in Sickle Cell Anemia, the most common adverse reactions were hematologic, with neutropenia, and low reticulocyte and platelet levels necessitating temporary cessation in almost all patients. Hematologic recovery usually occurred in two weeks. Other…
Who shouldn’t take Droxia
DROXIA is contraindicated in patients who have demonstrated a previous hypersensitivity to hydroxyurea or any other component of its formulation. In patients who have demonstrated a previous hypersensitivity to hydroxyurea or any other component of its formulation. ( 4 )
Droxia drug interactions
Antiretroviral drugs. (7.1) Laboratory Test Interference. ( 7.2 ) 7.1 Increased Toxicity with Concomitant Use of Antiretroviral Drugs Pancreatitis In patients with HIV infection during therapy with hydroxyurea and didanosine, with or without stavudine, fatal and nonfatal pancreatitis have occurred. Hydroxyurea is not indicated for the treatment of HIV infection; however, if patients with HIV infection are treated with hydroxyurea, and in particular, in combination with didanosine and/or stavudine, close monitoring for signs and symptoms of pancreatitis is recommended. Permanently discontinue therapy with DROXIA in patients who develop signs and symptoms of pancreatitis. Hepatotoxicity Hepatotoxicity and hepatic failure resulting in death have been reported during postmarketing surveillance in patients with HIV infection treated with hydroxyurea and other antiretroviral drugs. Fatal hepatic events were reported most often in patients treated with the combination of hydroxyurea, didanosine, and stavudine. Avoid this combination. Peripheral Neuropathy Peripheral neuropathy, which was severe in some cases, has been reported in patients with HIV infection receiving hydroxyurea in combination with antiretroviral drugs, including didanosine, with or without stavudine. 7.2 Laboratory Test Interference Interference with Uric Acid, Urea, or Lactic Acid Assays Studies have shown that there is an analytical interference of hydroxyurea with the enzymes (urease, uricase, and lactate dehydrogenase) used in the determination of urea, uric acid, and lactic acid, rendering falsely elevated results of these in patients treated with hydroxyurea. Interference with Continuous Glucose Monitoring Systems Hydroxyurea may falsely elevate sensor glucose results from certain continuous glucose monitoring (CGM) systems and may lead to hypoglycemia if sensor glucose results are relied upon to dose insulin. If a patient using a CGM is to be prescribed hydroxyurea, consult with the CGM prescriber about alternative glucose monitoring methods.
Every hydroxyurea product we track (4)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | Not yet rated | Prescription | Capsule | Generic | $6 | View → | |
| 2 | Not yet rated | Prescription | Capsule | Generic | $6 | View → | |
| 3 | Not yet rated | Prescription | Tablet | Generic | $6 | View → | |
| 4 | Not yet rated | Prescription | Solution | Generic | $6 | View → |
What hydroxyurea pills look like
Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.
How long hydroxyurea keeps
The date on a sealed pack is not the only one: some hydroxyurea labels start a second clock once the product is opened or mixed, as short as 12 weeks.
Does hydroxyurea expire? The in-use limits and storage rules from its labelsHydroxyurea and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for hydroxyurea: levels in milk, effects in breastfed infants, and the drugs it would consider insteadMost sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy, although the evidence for this recommendation for hydroxyurea is very weak. A clinical study and a pharmacokinetic model indicate that hydroxyurea is acceptable during breastfeeding. Avoiding breastfeeding during the first 3 hours after a dose can markedly decrease the infant dose. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk.
National Institute of Child Health and Human Development, record revised March 15, 2026. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about hydroxyurea
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 14,864 reports naming hydroxyurea, and the FDA flagged 72% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- sickle cell anaemia with crisis1,260 reports
- fatigue1,159 reports
- diarrhoea1,120 reports
- nausea1,010 reports
- headache833 reports
- haemoglobin decreased683 reports
- anaemia674 reports
- pyrexia602 reports
Read these as a signal, not a rate. A report does not mean hydroxyurea caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
How long hydroxyurea stays in your system
The elimination half-life of hydroxyurea is about 2 to 4 hours. The SIKLOS label states this under "Elimination" in §12.3 — it is the elimination half-life, and the label reports only this one phase (it does not break out a separate distribution/alpha phase). Hydroxyurea is not a prodrug, and the label names no active metabolite: up to 60% of an oral dose is cleared by saturable liver metabolism plus a minor breakdown route by urease from gut bacteria, with about 40% of the dose recovered in urine. Kidney impairment matters — exposure (mean AUC) was 64% higher in people with creatinine clearance under 60 mL/min and in those with end-stage renal disease, and the label directs a dose reduction in those patients. For liver impairment, the label explicitly says there are no data supporting specific dose-adjustment guidance. It gives no separate half-life for older adults; it notes pharmacokinetics are similar between children (4 to 17 years) and adults. Worth knowing: most other hydroxyurea labels (Hydrea, Droxia, Xromi, and the generics) state no half-life at all — SIKLOS is the label that carries this number. This is a plasma-clearance figure, not a drug-test detection window and not dosing guidance; hydroxyurea's biological effect on blood counts outlasts the drug's time in plasma.
SIKLOS (hydroxyurea) tablets — FDA label, §12.3 Pharmacokinetics (DailyMed) ↗Half-life is how long the body takes to clear half a dose. It is not the same as how long a drug test can detect it, and it varies with age, kidney and liver function.
Related calculators
Frequently asked questions
What is Droxia?
Droxia (Hydroxyurea) is a medication used to treat Brain Neoplasms, Non-Small-Cell Lung Carcinoma, Renal Cell Carcinoma, Squamous Cell Carcinoma.
How long does hydroxyurea stay in your system?
The elimination half-life of hydroxyurea is about 2 to 4 hours — that is how long the body takes to clear half of a dose. The SIKLOS label states this under "Elimination" in §12.3 — it is the elimination half-life, and the label reports only this one phase (it does not break out a separate distribution/alpha phase). Hydroxyurea is not a prodrug, and the label names no active metabolite: up to 60% of an oral dose is cleared by saturable liver metabolism plus a minor breakdown route by urease from gut bacteria, with about 40% of the dose recovered in urine. Kidney impairment matters — exposure (mean AUC) was 64% higher in people with creatinine clearance under 60 mL/min and in those with end-stage renal disease, and the label directs a dose reduction in those patients. For liver impairment, the label explicitly says there are no data supporting specific dose-adjustment guidance. It gives no separate half-life for older adults; it notes pharmacokinetics are similar between children (4 to 17 years) and adults. Worth knowing: most other hydroxyurea labels (Hydrea, Droxia, Xromi, and the generics) state no half-life at all — SIKLOS is the label that carries this number. This is a plasma-clearance figure, not a drug-test detection window and not dosing guidance; hydroxyurea's biological effect on blood counts outlasts the drug's time in plasma. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.
Can you take hydroxyurea with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run hydroxyurea against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is hydroxyurea sold under?
We track 4 hydroxyurea-containing products in the U.S.: Droxia, Hydrea, Siklos and Xromi. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does hydroxyurea come in?
Across the brands we track, hydroxyurea is currently marketed as capsule, tablet and solution, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic hydroxyurea?
We do not currently list a generic-labelled hydroxyurea product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Hydroxyurea: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/hydroxyurea
- MLA
- “Hydroxyurea: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/hydroxyurea.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for hydroxyurea on DailyMed (NIH) ↗ — including its boxed warning in full.