Hydroxyurea
**Hydroxyurea** is an oral **antineoplastic** (anti-cancer) agent primarily used in veterinary medicine to treat myeloproliferative disorders. Key indications include: * **Polycythemia vera**: Reduces excessive red blood cell production. * **Chronic myelogenous leukemia (CML)**: Often utilized when patients are no longer responsive to busulfan. * **Mast cell tumors (Mastocytomas)**. * **Cardiovascular shunts**: Used adjunctively in right-to-left shunting patent ductus arteriosus (PDA) or Tetralogy of Fallot to reduce hematocrit and alleviate hyperviscosity. * **Feline hypereosinophilic syndrome** and adjunctive treatment for **canine meningiomas**. > **Clinical Pearl**: Because it is a chemotherapy agent, strict handling precautions must be observed by both veterinary staff and pet owners to prevent accidental exposure.
Mecanismo: Hydroxyurea is an **S-phase specific** antimetabolite. * It specifically inhibits the enzyme **ribonucleotide reductase** → blocks the conversion of ribonucleotides to deoxyribonucleotides → halts **DNA synthesis** without significantly interfering with RNA or protein synthesis. * Cells are arrested at the **G1-S border**. * It also inhibits **urease** (though less potently than acetohydroxamic acid) and can stimulate the production of fetal hemoglobin.
Dosificación por especie
- Polycythemia vera; chronic myelogenous leukemia · 25 mg/kg · PO · 3 times per week
- Polycythemia vera · 10-15 mg/kg · PO · twice daily · Initially; once the hematocrit is below 60% give every other day.
- Polycythemia vera · 30 mg/kg · PO · once daily · for one week · Then 15 mg/kg once daily until remission; then taper to lowest effective frequency by monitoring hematocrit. Cats must be monitored more frequently than dogs.
- Polycythemia vera; chronic myelogenous leukemia · 50 mg/kg · PO · 3 times per week
- Polycythemia vera · 20-25 mg/kg · PO · twice daily · Initially; once the hematocrit is below 60% give every other day.
- Polycythemia vera · 30 mg/kg · PO · once daily · for one week · Then 15 mg/kg once daily until remission; then taper to lowest effective frequency by monitoring hematocrit.
- Polycythemia vera · 50-80 mg/kg · PO · every 3 days
- Chronic myelogenous leukemia · 50 mg/kg · PO · q24h · for 1-2 weeks · Then every other day.
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- Pre-existing severe anemia or bone marrow depression
- History of urate stones
- Current severe infection
- Impaired renal function
- Patients who have recently received other chemotherapy or radiotherapy
- Pregnancy (proven teratogen)
Efectos adversos
- Bone marrow depression (anemia, thrombocytopenia, leukopenia)
- GI effects (anorexia, vomiting, diarrhea)
- Stomatitis
- Sloughing of nails
- Alopecia
- Dysuria
- Pulmonary fibrosis
- Methemoglobinemia (especially in cats at high doses >500 mg)
Interacciones farmacológicas
- Bone marrow depressant drugs (e.g., chloramphenicol, flucytosine, amphotericin B, colchicine, other antineoplastics) · May cause additive myelosuppression when used concurrently with hydroxyurea.
- Allopurinol · Hydroxyurea may raise serum uric acid levels; allopurinol may be required to control hyperuricemia.
Monitoreo
- CBC with platelets at least every 1-2 weeks until stable; then every 3 months
- BUN/Serum Creatinine initially before starting treatment and then every 3-4 months
- Hematocrit levels (to guide tapering of dose)
Sobredosis
Because of the potential toxicity of the drug, overdoses should be treated aggressively with gut emptying protocols employed when possible. **Cats** given hydroxyurea in doses greater than 500 mg (total) may develop **methemoglobinemia** (characterized by cyanosis, respiratory distress, and dark-colored blood). Contact an animal poison control center for further guidance.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.