ヒドロキシウレア
**ヒドロキシウレア**は、獣医学において主に骨髄増殖性疾患の治療に使用される経口**抗悪性腫瘍薬**（抗がん剤）です。 主な適応症： * **真性多血症**：過剰な赤血球の産生を抑えます。 * **慢性骨髄性白血病 (CML)**：ブスルファンが効かなくなった患者にしばしば使用されます。 * **肥満細胞腫**。 * **心血管シャント**：右左シャントを伴う動脈管開存症 (PDA) やファロー四徴症において、ヘマトクリット値を下げ、過粘稠度を緩和するための補助療法として使用されます。 * **猫好酸球増多症候群**および**犬の髄膜腫**の補助治療。 > **臨床上の注意**：これは抗がん剤であるため、誤って曝露するのを防ぐために、獣医療スタッフおよび飼い主は厳格な取り扱い上の注意を守る必要があります。
作用機序: 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.
動物種別の用量
- 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.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- 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)
有害事象
- 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)
薬物相互作用
- 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.
モニタリング
- 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)
過量投与
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 の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。