シタラビン
シタラビン（通称 **Ara-C**）は、主に犬や猫のリンパ網内系腫瘍、骨髄増殖性疾患（白血病）、および中枢神経系リンパ腫の治療に使用される合成ピリミジンヌクレオシド代謝拮抗薬です。 > **臨床のポイント：** 従来の腫瘍学にとどまらず、シタラビンは獣医神経学において、犬の**原因不明の髄膜脳炎（MUE）**や肉芽腫性髄膜脳炎（GME）に対する中心的な免疫抑制療法として広く利用されています。持続静脈内輸液（CRI）や高用量皮下注射プロトコルで投与した場合、血液脳関門を通過する能力があるため、中枢神経系の炎症性疾患に対して非常に有効です。
作用機序: Cytarabine is a cell-cycle phase-specific antimetabolite that acts principally during the **S-phase** (active DNA synthesis). * **Intracellular Conversion:** Cytarabine enters the cell and is phosphorylated into its active form, **cytarabine triphosphate**. * **Enzyme Inhibition:** This active metabolite competes with deoxycytidine triphosphate → incorporates into DNA → potently inhibits **DNA polymerase**. * **Result:** Inhibition of DNA synthesis and repair, leading to cell death in rapidly dividing cells. Under certain conditions, it may also block cells from transitioning from the G1 phase to the S phase.
動物種別の用量
- Susceptible neoplastic diseases · 100 mg/m2 · IV/SC · continuous infusion over 2-3 days or divided and given IV or SC for 2-4 days · 2-4 days · Dosed in mg/m2 (NOT mg/kg). Cats are generally dosed similarly to dogs.
- Neoplastic diseases · 200-300 mg/m2 (usually 1-1.5 grams per horse per dose) · SC/IM/IV · every 1-2 weeks · Consultation with a veterinary oncologist is encouraged before use.
- Susceptible neoplastic diseases · 100 mg/m2 · IV/SC · continuous infusion over 2-3 days or divided and given IV or SC for 2-4 days · 2-4 days · Dosed in mg/m2 (NOT mg/kg). Use only as a general guide.
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
- Hypersensitivity to cytarabine
- Pregnancy (potentially teratogenic and embryotoxic)
有害事象
- Myelosuppression (leukopenia, anemia, thrombocytopenia)
- Anorexia
- Nausea
- Vomiting
- Diarrhea
- Conjunctivitis
- Oral ulceration
- Neurotoxicity
- Hepatotoxicity
- Fever
- Anaphylaxis (rare)
薬物相互作用
- Digoxin · Cytarabine may decrease the amount of digoxin (tablets only) absorbed after oral dosing due to intestinal mucosa alterations; effect may persist for several days after cytarabine discontinuation.
- Flucytosine (5-FC) · Cytarabine may antagonize the anti-infective activity of flucytosine; monitor for decreased efficacy.
- Gentamicin · Cytarabine may antagonize the anti-infective activity of gentamicin; monitor for decreased efficacy.
モニタリング
- Efficacy (tumor response or resolution of neurologic signs)
- Hemograms (mandatory; monitor for myelosuppression, nadir typically at 5-7 days)
- Liver function tests (periodic)
- Kidney function tests (periodic)
過量投与
Efficacy and toxicity are dependent on both the dose and the rate of administration. In dogs, the IV LD50 is 384 mg/kg when given over 12 hours, but drops to 48 mg/kg when infused IV over 120 hours. In the event of an inadvertent overdose, aggressive supportive therapy should be instituted.
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。