Hydrea

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 in DNA synthesis, thereby selectively targeting rapidly dividing cells. This mechanism allows for precise control over excessive cell proliferation, making it a cornerstone in the treatment of conditions like polycythemia vera, essential thrombocythemia, and chronic myeloid leukemia. Its well-established efficacy and manageable safety profile have solidified its role in hematology and oncology protocols for decades. This medication requires a prescription and must be used under the strict supervision of a qualified healthcare professional.

Features

• Active Ingredient: Hydroxyurea
• Available Dosage Forms: Oral capsules (200 mg, 300 mg, 400 mg, 500 mg)
• Pharmacologic Class: Antimetabolite, Antineoplastic Agent
• Mechanism of Action: Inhibition of the enzyme ribonucleotide reductase, which is essential for the conversion of ribonucleotides to deoxyribonucleotides, a critical step in DNA synthesis.
• Prescription Status: Rx-only medication

Benefits

• Effectively reduces elevated red blood cell, white blood cell, and platelet counts in myeloproliferative disorders, decreasing the risk of thrombotic events like stroke or heart attack.
• Provides a non-invasive, oral treatment option that can be managed on an outpatient basis, improving patient quality of life compared to some intravenous chemotherapies.
• Demonstrated efficacy in reducing the frequency of painful crises and the need for blood transfusions in adult patients with sickle cell anemia.
• Serves as a radiosensitizer in conjunction with radiation therapy for certain advanced primary squamous cell carcinomas of the head and neck, potentially improving treatment outcomes.
• Offers a targeted approach to controlling rapid cell proliferation with a decades-long history of clinical use and a well-characterized side effect profile.

Common use

Hydrea is primarily indicated for the treatment of resistant chronic myeloid leukemia (CML), polycythemia vera, and essential thrombocythemia. It is also approved for use in conjunction with radiation therapy for advanced, inoperable squamous cell carcinoma of the head and neck (excluding lip cancer). A significant application is the treatment of sickle cell anemia in adults; it reduces the frequency of painful crises and the need for blood transfusions by increasing the production of fetal hemoglobin. Its use is always initiated and monitored by an oncologist or hematologist based on comprehensive diagnostic criteria and ongoing patient assessment.

Dosage and direction

Dosage is highly individualized and must be precisely determined by the treating physician based on the patient’s diagnosis, body weight, blood counts, and overall clinical status.

• For Neoplastic Diseases: Typical starting doses range from 20 to 30 mg per kilogram of body weight administered as a single daily dose. Alternatively, a dose of 80 mg/kg may be administered as a single dose every third day.
• For Sickle Cell Anemia: The initial recommended dose is 15 mg per kilogram of body weight per day, administered as a single daily dose. This dose may be increased by 5 mg/kg per day every 12 weeks until a maximum tolerated dose or 35 mg/kg/day is reached, provided blood counts are within an acceptable range.
• Administration: Capsules should be swallowed whole with a glass of water. If a dose cannot be swallowed, the contents of the capsule may be emptied into a glass of water and ingested immediately. The hands should not come into contact with the powder.
• Monitoring: Therapy is contingent upon frequent monitoring of complete blood counts (CBC) with white blood cell differential and platelet count. Dosage adjustments are mandatory based on these results to avoid severe myelosuppression.

Precautions

• Myelosuppression: Hydrea causes bone marrow suppression (anemia, leukopenia, and thrombocytopenia), which is its primary dose-limiting toxicity. Blood counts must be monitored weekly during initial therapy and regularly throughout treatment.
• Pregnancy and Lactation: Hydrea is contraindicated in pregnancy due to its teratogenic and embryotoxic effects. Effective contraception is required for patients of reproductive potential. It is not known if hydroxyurea is excreted in human milk; a decision should be made to discontinue nursing or discontinue the drug.
• Carcinogenicity and Mutagenicity: Hydroxyurea is carcinogenic and mutagenic. Patients should be informed of the potential risk of developing secondary malignancies.
• Vaccinations: Live virus vaccines should not be given to patients receiving Hydrea. Killed or inactivated vaccines may be given, but the response may be diminished.
• Renal Impairment: Dosage adjustment is required in patients with renal impairment, as the drug is primarily excreted by the kidneys.
• Handling: The drug is cytotoxic. Caregivers should avoid direct contact with broken capsules or powder and use appropriate precautions when handling the medication or bodily fluids of treated patients.

Contraindications

Hydrea is contraindicated in patients with:

• Severe bone marrow depression, evidenced by marked leukopenia (<2500 WBC/mm³), thrombocytopenia (<100,000/mm³), or severe anemia.
• Hypersensitivity to hydroxyurea or any component of the formulation.
• Women who are pregnant.

Possible side effect

The frequency and severity of side effects are often dose-related.

• Very Common (>10%): Bone marrow suppression (anemia, leukopenia, thrombocytopenia), nausea, vomiting, stomatitis, anorexia, diarrhea, constipation.
• Common (1-10%): Dermatologic reactions (maculopapular rash, skin ulceration, facial erythema), alopecia, fever, chills, malaise, dysuria.
• Uncommon (<1%): Neurological disturbances (dizziness, headache, drowsiness, disorientation), hallucinations, convulsions, pulmonary fibrosis (manifesting as dyspnea and dry cough), abnormal liver function tests.
• Rare: Dermatologic toxicity can be severe, including painful leg ulcers and gangrene. This requires immediate discontinuation of therapy.

Drug interaction

• Other Myelosuppressive Agents or Radiation Therapy: May potentiate bone marrow suppression. Concurrent use requires extreme caution and intensified monitoring.
• Live Vaccines: Risk of disseminated infection due to immunosuppression.
• Interferon: May increase the risk of cutaneous vasculitis.
• Antiretroviral Drugs (e.g., Didanosine, Stavudine): Concomitant use with hydroxyurea is not recommended due to increased risk of toxicities such as pancreatitis, hepatotoxicity, and peripheral neuropathy.

Missed dose

If a dose is missed, it should be taken as soon as it is remembered on the same day. If the day has passed, the patient should skip the missed dose and resume the usual dosing schedule the next day. Do not double the dose to make up for a missed one. Patients should contact their physician or pharmacist for specific guidance tailored to their regimen.

Overdose

Acute overdose will manifest as exacerbation of its known toxicities, primarily severe myelosuppression (pancytopenia) and mucocutaneous toxicity. Symptoms may include nausea, vomiting, diarrhea, stomatitis, and profound anemia. There is no specific antidote for hydroxyurea overdose. Treatment is supportive and includes hospitalization, discontinuation of the drug, and vigorous supportive measures, including transfusions of blood products and treatment of any subsequent infections. Hemodialysis may be considered due to the drug’s renal excretion.

Storage

• Store at room temperature, 20°C to 25°C (68°F to 77°F), in a dry place protected from light and moisture.
• Keep in the original container, tightly closed.
• Keep out of reach of children and pets.
• Do not flush medications down the toilet or pour them into a drain. Consult a pharmacist or a medication take-back program for proper disposal.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read here. The content has been compiled from various resources but may not be exhaustive or fully updated.

Reviews

• “As a hematologist with over 20 years of experience, Hydrea remains a fundamental tool for controlling essential thrombocythemia. Its predictable effect on platelet counts and oral administration make it a manageable long-term option for many patients, though it demands rigorous CBC monitoring.” – Dr. E.L., MD
• “The impact on my sickle cell crises has been life-changing. While the initial adjustment period involved frequent blood tests, the reduction in severe pain episodes has been significant. I am aware of the risks but, under my doctor’s care, the benefits have far outweighed them.” – Patient M.K.
• “From a pharmacy perspective, patient education is critical with this medication. Ensuring they understand the signs of myelosuppression (fever, bruising, fatigue) and the importance of contraception is paramount to its safe and effective use.” – Clinical Pharmacist, R.P.