Hydroxyurea (Hydrea, Droxia, Siklos, and others)

How Medicare covers it

Part D (forms used at home). Part A during a covered inpatient stay. No Part B clinician-administered form in the CMS Part B spending file.

What it treats

Hydroxyurea (this label: Hydrea 500 mg capsules) is an antimetabolite — a chemotherapy-type medicine. The pinned label is indicated for resistant chronic myeloid leukemia (CML) and for locally advanced squamous cell carcinomas of the head and neck (excluding the lip) used together with chemoradiation. The wider package behind this page also includes the sickle-cell products (Droxia, Siklos, Xromi), whose own labels cover reducing painful crises in sickle cell disease.

What it is for, in depth

From the pinned Hydrea label's Indications section: treatment of resistant chronic myeloid leukemia, and locally advanced squamous cell carcinomas of the head and neck (excluding the lip) in combination with chemoradiation. It is a later-line cancer medicine — 'resistant' CML means the leukemia no longer responds to other treatment — and a radiation partner in head and neck cancer, where the label's pharmacology explains it holds tumor cells in the stage where radiation works best and hinders repair of radiation-damaged cells. Who it is prescribed for, in this package, is broader than the pinned label: the formulary data behind this page also covers Droxia and Siklos (hydroxyurea capsules/tablets) and Xromi (oral solution), the sickle-cell disease products named in this package's record, which are prescribed to reduce painful crises in sickle cell disease — that use rests on those products' own labels, not on the Hydrea label pinned here. Forms in the package: 500 mg generic/Hydrea capsules, Droxia 200/300/400 mg capsules, Siklos 100/1000 mg tablets, and the Xromi oral solution.

How it works

The label says the precise mechanism of its anti-cancer effect is not fully described, but the evidence supports that hydroxyurea immediately inhibits DNA synthesis by acting as a ribonucleotide reductase inhibitor, without interfering with RNA or protein synthesis. Because cancer cells cannot copy their DNA, they cannot divide. The same DNA-synthesis block explains why it can harm a developing fetus, and why it also suppresses the bone marrow, where blood cells are made.

How it is taken

Oral capsules (this label: 500 mg). Treatment is individualized based on tumor type, disease state, response, and patient risk factors. Blood counts are checked at baseline and throughout treatment, and the dose is interrupted or reduced when the marrow is suppressed. In patients with kidney impairment (creatinine clearance under 60 mL/min), the Hydrea dose is reduced by 50%. It must not be given if bone marrow function is markedly depressed.

Common side effects

The label extract's adverse-reactions section names the clinically significant reactions detailed in its warnings rather than a frequency table: myelosuppression (lowered blood counts), hemolytic anemia (breakdown of red blood cells), secondary malignancies, vasculitic toxicities (blood-vessel inflammation, including skin ulceration), pancreatitis/hepatotoxicity/neuropathy risks with certain HIV medicines, radiation recall (skin redness in previously irradiated areas), macrocytosis (enlarged red blood cells), and pulmonary (lung) toxicity.

Serious warnings

This pinned SPL carries no boxed-warning section (verified directly against the live SPL), but its Warnings and Precautions are grave and are stated here plainly. Myelosuppression: hydroxyurea suppresses the bone marrow — do not give it if marrow function is markedly depressed; blood counts are monitored throughout treatment and the dose is interrupted or reduced as necessary. Hemolytic anemia: if hemolysis persists, the drug is discontinued. Malignancies: patients are advised to protect themselves from sun exposure and are monitored for secondary malignancies. Embryo-fetal toxicity: it can cause fetal harm — patients are advised of the risk to a fetus and to use effective contraception; women are advised not to breastfeed. Vasculitic toxicities require stopping the drug. Live vaccines are to be avoided. In patients with HIV on antiretroviral drugs, pancreatitis, liver toxicity, and neuropathy have occurred. Older patients may need a lower dose and kidney-function monitoring.

Who should be careful

Anyone with markedly depressed bone marrow function (the drug must not be given); people with kidney impairment (dose cut in half at creatinine clearance under 60); people who could become pregnant or father a pregnancy (fetal harm — effective contraception advised; no breastfeeding); people with HIV taking antiretroviral drugs; people who previously received radiation (radiation recall); older adults (dose selection with care, kidney monitoring); and anyone due a live vaccine (avoid).

Major interactions

The label's interaction warnings center on antiretroviral drugs: with concomitant use in patients with HIV infection, pancreatitis, hepatotoxicity (liver harm), and peripheral neuropathy have occurred — patients are monitored for signs and symptoms, and Hydrea is discontinued and treatment implemented if they occur. The label also flags interference with certain laboratory tests.

Cost and saving notes

Hydroxyurea is an old generic medicine, but in the CMS data behind this page it most often sits on a higher non-preferred tier (see the tier section) — the sickle-cell branded forms in this package are priced very differently from the plain generic capsule. If cost is a barrier, confirming the plan covers the generic capsule form, asking about a tier exception, and Extra Help for people with limited income are the factual routes.

Why it is in its tier

Hydroxyurea (Hydrea, Droxia, Siklos, and others) sits on Tier 4 in 64.77% of the plans that list it (3559 of 5495 listing plans). Tier 4 is the non-preferred tier — higher copays or coinsurance. The data-visible drivers: It is sold both as a brand product and in generic form, and the CMS dashboard puts its average Part D spending at about $117 per beneficiary for 2024 — a relatively low-cost drug, which matches where plans place it. It is listed by 100.0% of Part D plans. The tier shown is the most common one; individual plans vary.

Sources

• HYDREA (HYDROXYUREA) CAPSULE [H2-PHARMA LLC] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Hydroxyurea

What official patient guides say

Hydroxyurea comes as a capsule to take by mouth (the form in this package). It is usually taken once a day with a glass of water; for certain types of cancer it may be taken once every third day — your doctor will tell you how often to take it. Take it at around the same time every day, exactly as directed. Swallow the capsules whole; do not split, chew, or crush them. Wear rubber or latex gloves when you handle the capsules so the medication does not touch your skin, and wash your hands before and after you touch the bottle or the medication. If powder spills, wipe it up with a damp disposable towel, seal it in a plastic bag, and throw it away out of reach of children and pets. Your doctor may delay treatment or adjust your dose based on your response and side effects, and may tell you to take folic acid to decrease some side effects. Do not stop taking it without talking to your doctor. If you miss a dose, take it as soon as you remember; if it is almost time for the next dose, skip it and go back to your regular schedule. Do not take a double dose. Keep it in the container it came in, tightly closed and out of reach of children and pets. Store it at room temperature, away from extra heat and moisture, and not in the bathroom.

Source: MedlinePlus — Hydroxyurea

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is 0.18447 per unit (HYDROXYUREA 500 MG CAPSULE) — about nan for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-07

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 5,495 list Hydroxyurea (Hydrea, Droxia, Siklos, and others) — 100% of plans. Most of those plans put it on Tier 4: 3,559 plans, 64.8% of the plans that list it. Other plans place it on Tier 3 (895 plans), Tier 2 (869 plans) or Tier 1 (172 plans). For example: Aetna Medicare Dual Extra (HMO D-SNP) puts it on Tier 4; Aetna Medicare Dual Extra Care (PPO D-SNP) puts it on Tier 4; Aetna Medicare Value Plus (PPO) puts it on Tier 4. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan';s deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.