バクロフェン
バクロフェンは中枢性の骨格筋弛緩薬です。獣医療では主に犬の機能性尿閉の管理（尿道括約筋の緊張低下）に適応外使用されます。 **臨床上のポイント:** * 動物における安全域は非常に狭く、人間の薬剤の誤飲による中毒が頻繁に報告されています。 * **猫への使用は厳禁です。** * 治療用量では血液脳関門を通過しにくいため中枢作用は限定的ですが、大量の過剰投与は重度の中枢神経抑制を引き起こします。
作用機序: Baclofen is a structural analog of the inhibitory neurotransmitter **GABA** (gamma-aminobutyric acid). It acts primarily as a **GABA-B receptor agonist** at the spinal cord level. * Activation of **GABA-B receptors** → hyperpolarization of primary afferent nerve terminals → inhibition of the release of excitatory neurotransmitters (such as glutamate and aspartate). * This reduces **gamma efferent neuronal activity**, decreasing the frequency and amplitude of muscle spasms. * In the lower urinary tract, it specifically reduces **striated sphincter tone** in the urethra, facilitating bladder emptying.
動物種別の用量
- To treat urinary retention by decreasing urethral resistance · 1-2 mg/kg · PO · q8h
- To treat urinary retention by decreasing urethral resistance · 5-10 mg (total dose) · PO · q8h
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 (strictly not recommended)
- Hypersensitivity to baclofen
有害事象
- Sedation
- Weakness
- Pruritus
- Salivation
- Gastrointestinal distress (nausea, abdominal cramping)
薬物相互作用
- CNS Depressants · May cause additive CNS depression
モニタリング
- Efficacy (improvement in urination)
- Adverse effects (sedation, weakness, GI signs)
過量投与
Baclofen has a narrow margin of safety in dogs. * **Toxicity Thresholds:** Deaths have been reported at doses as low as **8 mg/kg**. Clinical signs can appear at doses as low as **1.3 mg/kg**. * **Clinical Signs:** Vomiting, depression, vocalization, hypersalivation, ataxia, hypotonia, muscle twitching, hypothermia, and lethargy. Massive overdoses may cause respiratory depression, coma, or seizures. * **Onset & Duration:** Signs can occur 15 minutes to 7 hours post-ingestion and persist for hours to days. * **Treatment:** * In alert patients, empty the gut (emesis/lavage). * **Avoid** magnesium-containing saline cathartics (may compound CNS depression). * Forced fluid diuresis may enhance excretion. * Mechanical ventilation for respiratory depression. * **Cyproheptadine** (1.1 mg/kg PO or PR) may alleviate vocalization and disorientation. * Atropine may improve ventilation, HR, BP, and body temperature. * Diazepam for seizures. * **Intravenous Lipid Emulsion (ILE)** may be useful as baclofen is lipid-soluble.
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。