Hydrea (hydroxyurea) is an oral chemotherapeutic agent specifically formulated for the management of certain chronic blood disorders and solid tumors. As an antimetabolite, it exerts its therapeutic effect by inhibiting ribonucleotide reductase, a key enzyme necessary for DNA synthesis. This targeted mechanism allows for the controlled reduction of rapidly dividing cells, particularly in the bone marrow, making it a cornerstone therapy for conditions like polycythemia vera, essential thrombocythemia, and chronic myeloid leukemia. Its well-established efficacy profile and oral administration offer a significant advantage in long-term disease management protocols, providing clinicians with a reliable tool to control hematological parameters and reduce thrombotic risks associated with myeloproliferative neoplasms.

Features

• Active Ingredient: Hydroxyurea
• Available Strengths: 500 mg capsules
• Pharmacological Class: Antimetabolite, antineoplastic agent
• Mechanism of Action: Inhibition of ribonucleotide reductase
• Administration: Oral
• Bioavailability: Rapid and nearly complete gastrointestinal absorption
• Half-life: Approximately 3-4 hours
• Metabolism: Hepatic (partial)
• Excretion: Primarily renal

Benefits

• Effectively reduces elevated hematocrit and platelet counts in polycythemia vera, decreasing the risk of thrombotic events
• Provides symptomatic relief from complications of sickle cell disease by increasing fetal hemoglobin production and reducing vaso-occlusive crises
• Offers convenient oral administration compared to intravenous chemotherapeutic alternatives
• Demonstrates a predictable response pattern with dose-dependent effects on blood counts
• Serves as an effective cytoreductive therapy while maintaining relatively manageable side effects compared to other chemotherapeutic agents
• Can be used as a bridging therapy before stem cell transplantation in certain hematological malignancies

Common use

Hydrea is primarily indicated for the treatment of polycythemia vera, particularly in patients with a history of thrombotic events or those who cannot tolerate phlebotomy. It is extensively used in the management of essential thrombocythemia to control thrombocytosis and associated symptoms. In sickle cell disease, it is employed to reduce the frequency of painful crises and the need for blood transfusions. Additionally, it finds application as part of combination therapy in chronic myeloid leukemia, particularly when interferon therapy is not suitable. Off-label uses include the treatment of certain solid tumors and as a radiosensitizer in head and neck cancers.

Dosage and direction

Dosage must be individualized based on patient response, tolerance, and blood counts. For polycythemia vera: Initial dose is 15-20 mg/kg/day as a single dose. Maintenance dose is typically adjusted to keep hematocrit below 45% and platelet count within normal range. For essential thrombocythemia: 15-20 mg/kg/day, adjusted to maintain platelet count below 600,000/μL. For sickle cell disease: Initial dose is 15 mg/kg/day, increased by 5 mg/kg/day every 12 weeks to maximum of 35 mg/kg/day if blood counts are acceptable. Capsules should be swallowed whole with water; if unable to swallow whole, contents may be emptied into water and consumed immediately. Administration at the same time each day is recommended. Regular monitoring of complete blood counts is essential, typically weekly during dose adjustment and monthly during maintenance therapy.

Precautions

Hydrea requires careful hematological monitoring due to its myelosuppressive effects. Complete blood counts should be performed weekly during initial therapy and regularly during maintenance. Use with caution in patients with renal impairment; dosage reduction is necessary. Hepatic function should be monitored periodically. Patients should be advised to maintain adequate hydration. Due to potential teratogenic effects, appropriate contraception must be used during treatment. Skin should be protected from excessive sun exposure as photosensitivity may occur. Regular monitoring for signs of secondary malignancies is recommended during long-term therapy. Dental status should be assessed before initiation as mucositis may occur.

Contraindications

Hydrea is contraindicated in patients with severe bone marrow suppression evidenced by leukopenia (WBC <2500/μL), thrombocytopenia (platelets <100,000/μL), or severe anemia. It should not be used in patients with hypersensitivity to hydroxyurea or any component of the formulation. Contraindicated in women who are pregnant or breastfeeding due to potential fetal harm. Should not be administered to patients with severe renal impairment (creatinine clearance <30 mL/min) without significant dose adjustment and close monitoring. Not recommended for patients with active infections that may be exacerbated by myelosuppression.

Possible side effect

Common (≥10%): Myelosuppression (anemia, leukopenia, thrombocytopenia), nausea, vomiting, diarrhea, stomatitis, mucositis, skin reactions (rash, dry skin), alopecia, drowsiness, fever Less common (1-10%): Dermatological changes (hyperpigmentation, violet nail beds), gastrointestinal disturbances, elevated liver enzymes, headache, dizziness, constipation Rare (<1%): Pulmonary fibrosis, hepatotoxicity, neurological symptoms (seizures, hallucinations), vasculitic ulcers, pancreatitis, secondary malignancies with long-term use Sickle cell disease-specific: Leg ulcers, particularly in patients receiving higher doses for extended periods

Drug interaction

Hydrea interacts significantly with other myelosuppressive agents (including other chemotherapy drugs, azathioprine, and clozapine), potentially increasing the risk of bone marrow suppression. Concurrent use with live vaccines is not recommended due to immunosuppression. May enhance the toxicity of other antiretroviral drugs in HIV treatment. Interaction with drugs that affect renal function may alter hydroxyurea clearance. Use with caution alongside medications that cause hepatotoxicity. May potentiate the effects of radiation therapy when used as a radiosensitizer. Monitor closely when administered with drugs that undergo extensive hepatic metabolism.

Missed dose

If a dose is missed, it should be taken as soon as remembered on the same day. However, if it is near the time for the next scheduled dose, the missed dose should be skipped. Patients should never double the dose to make up for a missed one. Consistent dosing is important for maintaining therapeutic effect, so establishing a routine is recommended. If multiple doses are missed or uncertainty exists about dosing schedule, patients should contact their healthcare provider for guidance rather than attempting to adjust dosing independently.

Overdose

Acute overdose may manifest as exacerbation of expected toxic effects, particularly severe myelosuppression with pancytopenia, mucositis, and gastrointestinal toxicity. Symptoms may include extreme fatigue, fever, chills, sore throat, bleeding, or bruising. Management is primarily supportive and should include immediate discontinuation of the drug, hospitalization for monitoring, and aggressive supportive care including transfusions as needed. Hemodialysis may be considered in severe cases as hydroxyurea is partially dialyzable. There is no specific antidote. Treatment should focus on managing specific symptoms and supporting bone marrow recovery.

Storage

Store at controlled room temperature (20-25°C or 68-77°F) in the original container. Protect from moisture and light. Keep tightly closed and out of reach of children and pets. Do not store in bathroom cabinets where humidity levels may fluctuate. Unused medication should be disposed of properly through take-back programs or according to local regulations. Do not flush medications down the toilet or pour into drains unless specifically instructed to do so. Capsules should be kept in their original packaging until administration to maintain stability.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Treatment decisions must be made by qualified healthcare professionals based on individual patient circumstances. The prescribing physician should be consulted for specific dosage recommendations and monitoring requirements. Actual clinical use may differ from described indications based on evolving medical evidence and individual patient factors. Patients should not alter their treatment regimen without consulting their healthcare provider.

Reviews

Clinical studies consistently demonstrate Hydrea’s efficacy in controlling hematological parameters in myeloproliferative disorders, with response rates of 80-90% in polycythemia vera for hematocrit control. In sickle cell disease, trials show approximately 50% reduction in painful crises and reduced need for transfusions. Long-term follow-up studies indicate maintained efficacy with appropriate dose adjustments. Patient-reported outcomes generally reflect improved quality of life due to reduced disease-related complications, though side effect management remains an important consideration in treatment continuity. The drug’s well-characterized safety profile and oral administration are frequently cited advantages in clinical practice.