氟美吡唑 (Fomepizole)
**氟美吡唑**（又稱 4-甲基吡唑或 4-MP）是一種合成解毒劑，在獸醫學中主要用於治療犬貓的**乙二醇（防凍液）中毒**。 關鍵臨床重點： * **時效性**：若在犬隻誤食後 8 小時內給藥，效果極佳。對於貓，則需要顯著更高的劑量，且必須在誤食後 3 小時內給藥，以防止致命的腎臟損傷。 * **機制**：它能防止有毒代謝物的形成，而非清除母體化合物。 * **臨床提示**：一旦出現氮血症（腎功能指數升高），預後將急劇下降，但仍可在誤食後 36 小時內給予氟美吡唑以阻止進一步損傷，同時進行支持性治療（如血液透析）。 * **成本與取得**：治療費用可能非常高昂（特別是對於大型犬），且在急診環境中，藥物是否能迅速取得通常是一大限制因素。
作用機制: Fomepizole acts as a potent, competitive inhibitor of **alcohol dehydrogenase (ADH)**, the primary enzyme responsible for the initial metabolism of ethylene glycol. **The Toxic Pathway:** Ethylene Glycol → (via **ADH**) → Glycoaldehyde → Glycolate → Glyoxalic Acid → Oxalic Acid. *Note: Oxalic acid binds with systemic calcium to form calcium oxalate crystals, which precipitate in the renal tubules causing acute tubular necrosis and severe metabolic acidosis.* **Fomepizole's Action:** By competitively binding to **ADH** with an affinity roughly 8,000 times greater than that of ethylene glycol, fomepizole effectively blocks the first step of this cascade. * Ethylene glycol remains unmetabolized in the bloodstream. * The parent compound (which is only mildly CNS-depressant) is then safely and slowly excreted unchanged in the urine. * This prevents the life-threatening metabolic acidosis and acute kidney injury associated with the toxic metabolites.
各物種劑量
- For treatment of ethylene glycol toxicity · Initially, 125 mg/kg slow IV ; at 12, 24, 36 hours give 31.25 mg/kg IV . · IV · Specific intervals (0, 12, 24, 36 hours) · 36 hours · Cats must be treated within 3 hours of ingestion. Treat supportively with supplemental fluids. Cats whose treatment began 4 hours post ethylene glycol had 100% mortality.
- For treatment of ethylene glycol toxicity · Initially load at 20 mg/kg IV ; at 12 hours post initial dose give 15 mg/kg IV ; at 24 hours post initial dose give another 15 mg/kg IV and at 36 hours after initial dose give 5 mg/kg; may give additional 5 mg/kg doses as necessary · IV · Specific intervals (0, 12, 24, 36 hours) · 36+ hours · May give additional 5 mg/kg doses as necessary if animal has not recovered or has additional ethylene glycol in blood.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- No labeled contraindications, but use with caution if the patient is already receiving ethanol therapy.
不良反應
- Vein irritation and phlebosclerosis (if given rapidly or undiluted)
- Anaphylaxis (rare)
- Mild sedation (particularly in cats)
藥物相互作用
- Ethanol · Fomepizole inhibits alcohol dehydrogenase; ethanol metabolism is reduced significantly and alcohol poisoning (CNS depression, coma, death) can occur. Concurrent use is generally not recommended. If used together, mandatory monitoring of ethanol blood levels is required.
監測
- Ethylene glycol blood levels (to document diagnosis and determine if therapy can be discontinued after 36 hours)
- Blood gases (acid-base status)
- Serum electrolytes
- Hydration status
- Renal function tests (Urine output, urinalysis, BUN, serum creatinine)
- Body temperature (especially in cats)
過量
Overdosage may cause significant **CNS depression**. There is no specific antidote or treatment recommended for fomepizole overdose; provide supportive care as needed.
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。