羥基脲
**羥基脲 (Hydroxyurea)** 是一種口服**抗腫瘤**（抗癌）藥物，在獸醫學中主要用於治療骨髓增生性疾病。 主要適應症包括： * **真性紅血球增多症 (Polycythemia vera)**：減少過多的紅血球生成。 * **慢性骨髓性白血病 (CML)**：常在病患對白消安 (busulfan) 不再有反應時使用。 * **肥大細胞瘤 (Mastocytomas)**。 * **心血管分流**：作為右向左分流的開放性動脈導管 (PDA) 或法洛氏四重症的輔助治療，以降低血球容積比並緩解血液過度黏稠。 * **貓嗜酸性球增多症候群**及**犬腦膜瘤**的輔助治療。 > **臨床提示**：由於這是一種化療藥物，獸醫人員和寵物主人必須嚴格遵守處理預防措施，以防止意外接觸。
作用機制: 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.
各物種劑量
- 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.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- 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)
不良反應
- 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)
藥物相互作用
- 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.
監測
- 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)
過量
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.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。