撲熱息痛 (乙醯胺酚)
撲熱息痛是一種中樞作用的止痛退燒藥，用於控制輕至中度的疼痛和發燒。與傳統的非類固醇消炎藥 (NSAIDs) 相比，它的抗發炎效果較差，但一般認為其腸胃道副作用較少，因此對於患有胃潰瘍的病患是一個有用的替代選擇。注射型撲熱息痛也可用於犬隻圍手術期的輔助鎮痛。 > **嚴重警告：** 貓咪絕對禁用撲熱息痛，因為貓缺乏安全代謝該藥物的酵素，會導致極高毒性甚至死亡。 **臨床提示：** 獲准的獸醫口服製劑 (Pardale-V) 含有可待因 (codeine)；然而，由於犬隻對鴉片類藥物具有很高的首過代謝率，該可待因成分的生物利用度極低，對鎮痛效果並無顯著貢獻。
作用機制: The exact mechanism of action remains partially unclear. It is proposed that its antipyretic and analgesic actions are due to: - Decreased **prostaglandin synthesis** specifically within the central nervous system (CNS). - Possible indirect actions on the **cannabinoid system**. Unlike traditional NSAIDs, it has minimal peripheral cyclooxygenase (COX) inhibition, which explains its lack of significant anti-inflammatory activity and reduced gastrointestinal toxicity.
各物種劑量
- Mild to moderate pain / Antipyretic · 10-20 mg/kg · PO/IV · q8h · 5-7 days (for acute pain) · For acute pain management, doses at the top of the range (20 mg/kg) can be used for up to 5-7 days.
- Mild to moderate pain (Pardale-V preparation) · 1 tablet per 12 kg body weight (equivalent to 33 mg/kg) · PO · q8h · Max 7 days before titrating down · Authorized dose for Pardale-V. After 7 days, titrate down to the lowest effective dose. Codeine component is not bioavailable.
- All indications · Do not use · PO/IV · N/A · N/A · Absolute contraindication. Fatal toxicosis due to methaemoglobinaemia.
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
- Cats (absolute contraindication due to fatal toxicosis)
- Patients with pre-existing severe hepatic impairment
不良反應
- Hepatotoxicity (dose-dependent)
- Methaemoglobinaemia (especially in cats)
- Facial edema
- Cyanosis
藥物相互作用
- Metoclopramide · Enhances the absorption of paracetamol, thereby enhancing its clinical and potentially toxic effects. · moderate
- Cytochrome P450 Inducers (e.g., Phenobarbital, certain NSAIDs) · May increase the production of toxic metabolites (NAPQI), enhancing the risk of hepatotoxicity. · major
監測
- Liver enzyme panel (ALT, AST, ALP, Bilirubin) if prolonged use or overdose is suspected
- Clinical signs of toxicity (jaundice, vomiting, lethargy)
- Mucous membrane color (monitoring for cyanosis/brown blood indicative of methaemoglobinaemia)
過量
Overdose of paracetamol causes severe liver damage. Metabolism produces the toxic intermediate **N-acetyl-p-aminobenzoquinonimine (NAPQI)**, which depletes hepatic glutathione, leading to hepatocyte cell death and centrilobular hepatic necrosis. In cats, it causes fatal methaemoglobinaemia. **Treatment:** - Decontamination (emesis/activated charcoal) if ingestion is recent. - **Antidote:** Oral **methionine** or IV **acetylcysteine (N-acetylcysteine)**. These are directed at replenishing hepatic glutathione stores to neutralize NAPQI, though clinical data in veterinary species is limited. - Supportive care (IV fluids, oxygen therapy, blood transfusions if severe methaemoglobinaemia occurs).
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