アセトアミノフェン
アセトアミノフェン（パラセタモール）は、合成非オピオイド鎮痛解熱薬です。 **臨床上のポイントと獣医学的背景：** * グルクロン酸抱合酵素が欠損しているため、毒性代謝物NAPQIが蓄積しやすく、**猫やフェレットにはいかなる用量でも極めて強い毒性**を示します。 * NSAIDsが禁忌（腎機能障害など）の場合に、犬や小型哺乳類の軽度から中等度の疼痛管理に時折使用されます。 * 臨床用量では末梢性の抗炎症作用はほとんどなく、血小板機能も阻害しません。 * 相乗的な鎮痛効果を得るため、オピオイド（コデイン、ヒドロコドンなど）との配合剤としてよく使用されます。
作用機序: Produces analgesia and antipyresis via weak, reversible, isoform-nonspecific inhibition of **cyclooxygenase (COX-3 / COX-1-v1)** in the central nervous system. **Mechanism Pathway:** Inhibition of central **COX** enzymes → decreased **prostaglandin** synthesis in the CNS → elevation of the pain threshold and alteration of the hypothalamic thermoregulatory center → analgesia and antipyresis. *Note: It lacks significant peripheral COX-1 or COX-2 inhibition, which explains its lack of anti-inflammatory and anti-platelet effects.*
動物種別の用量
- Analgesic (Rabbits) · 1-2 mg/mL in drinking water · PO · Ad libitum · Using Children's Tylenol. Effective for controlling low-grade nociception.
- Analgesic (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas) · 1-2 mg/mL in drinking water · PO · Ad libitum
- Analgesic · 15 mg/kg PO q8h · PO · q8h
- Analgesic · 10 mg/kg PO q12h · PO · q12h
- Analgesic · 10-15 mg/kg PO q12h · PO · q12h · 5 days
- Treatment of degenerative myelopathy (in German Shepherds) · 5 mg/kg PO (not to exceed 20 mg/kg per day) · PO · Daily
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
- Cats (at any dosage)
- Ferrets
- Sugar Gliders
- Hedgehogs
有害事象
- Methemoglobinemia (especially in cats and dogs at high doses)
- Hepatotoxicity (liver necrosis)
- Renal effects
- Gastrointestinal disturbances
- Facial and paw swelling (edema)
- Keratoconjunctivitis sicca (KCS)
- Cyanosis
- Hypothermia
薬物相互作用
- Other Analgesics · Chronic use with acetaminophen may lead to renal pathologies
- Barbiturates · Increased conversion of acetaminophen to hepatotoxic metabolites; potentially increased risk for hepatotoxicity
- Doxorubicin · May deplete hepatic glutathione, thereby leading to increased hepatic toxicity
- Halothane · Not recommended for postoperative analgesia in animals that received halothane anesthesia
- Isoniazid · Possible increased risk of hepatotoxicity
- Phenothiazines · Possible increased risk for hypothermia
- Propylene Glycol · May increase the severity of acetaminophen-induced methemoglobinemia or Heinz body formation
- Warfarin · Large doses may potentiate anticoagulant effects
モニタリング
- Liver enzymes (ALT, AST, ALP)
- Renal function (BUN, Creatinine)
- Hematologic parameters (CBC for methemoglobinemia or Heinz bodies)
- Clinical signs of toxicity (edema, cyanosis, lethargy)
過量投与
**Acute Toxicity & Overdose:** * **Clinical Signs:** Methemoglobinemia (brown blood/mucous membranes), liver necrosis, renal effects, facial and paw swelling, keratoconjunctivitis sicca (KCS), vomiting, lethargy, cyanosis, hypothermia. * **Species Differences:** Liver effects are more common in dogs; facial/paw swelling and methemoglobinemia are more common in cats. * **Treatment:** Standard gut emptying techniques (emesis/lavage) and activated charcoal if recent. Administer **acetylcysteine (NAC)** as a glutathione precursor to bind toxic metabolites. Supportive care includes **s-adenosyl methionine (SAMe)**, oxygen therapy, IV fluids, and blood transfusions or methylene blue for severe methemoglobinemia.
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。