グアイフェネシン
**グアイフェネシン**（別名グリセリルグアヤコールまたはGG）は、二つの目的を持つ薬理学的薬剤です。獣医学では、主に大型動物の短時間の麻酔処置（30〜60分）において、興奮のない導入と回復を促進するための**注射用筋弛緩薬**として利用されます。 * **麻酔補助薬**：横隔膜の機能を損なうことなく骨骼筋の弛緩を提供します。 * **経口去痰薬**：粘液を薄めることで呼吸器疾患を管理するために人および獣医学で使用されますが、臨床的有効性の決定的な証明については議論が残っています。 **臨床のポイント**：グアイフェネシン自体は麻酔薬ではありません。前麻酔薬および麻酔薬の作用を増強するため、バランス麻酔プロトコル（例：「トリプルドリップ」またはGKX）で使用する必要があります。軽度の固有の鎮痛および鎮静作用を持っています。
作用機序: * **Muscle Relaxation**: Acts centrally by depressing or blocking nerve impulse transmission at the **internuncial neuron** level of the subcortical areas of the brain, brainstem, and spinal cord → selective relaxation of skeletal muscles (including laryngeal and pharyngeal muscles, easing intubation) while sparing respiratory muscles. * **Expectorant Action**: Believed to stimulate gastric vagal receptors → triggers efferent parasympathetic reflexes → increases respiratory tract fluid volume and decreases mucus viscosity → facilitates removal of secretions via ciliary action and coughing.
動物種別の用量
- Using 'GKX' for induction/maintenance · Induce with 2.2 mL/kg IV. Maintain with approximately 2.2 mL/kg/hr IV · IV · CRI · Mix 1000 mL of 5% (50 mg/mL) guaifenesin with 1000 mg of ketamine ± 0-100 mg of xylazine.
- Using 'GKX' · Administer at a rate of 2-4 mL/kg · IV · Once then slowed · Given rapidly until animal is recumbent and then slowed to maintain desired anesthesia plane.
- Using 'GKX' for induction/maintenance · Induce with 2.2 mL/kg IV. Maintain with approximately 2.2 mL/kg/hr IV · IV · CRI · Mix 1000 mL of 5% (50 mg/mL) guaifenesin with 1000 mg of ketamine ± 0-100 mg of xylazine.
- Using 'GKX' · Administer at a rate of 2-4 mL/kg · IV · Once then slowed · Given rapidly until animal is recumbent and then slowed to maintain desired anesthesia plane.
- General · 55-110 mg/kg · IV · Once
- General anesthesia adjunct · 110 mg/kg · IV · Once · Give first 1/3-1/2 of dose until horse falls gently, then give remainder unless respiratory or cardiovascular effects are observed.
- Muscle relaxation in balanced anesthesia · A CRI of ketamine at 0.8-2.3 mg/kg/hr with guaifenesin at 18-60 mg/kg/hr · IV · CRI · May reduce MAC requirements by 50%.
投与経路
禁忌
- Concurrent use with physostigmine
- Concentrations greater than 5% in ruminants (due to hemolysis risk)
有害事象
- Mild hypotensive effect
- Increase in cardiac rate
- Thrombophlebitis (IV administration)
- Perivascular tissue reaction
- Hemolysis (especially in ruminants with >5% solutions)
- Increased gastrointestinal motility
薬物相互作用
- Physostigmine · Contraindicated in horses receiving guaifenesin; exact interaction mechanism not elucidated by manufacturer.
- Anticholinesterase agents (neostigmine, pyridostigmine, edrophonium) · Theoretically contraindicated based on the physostigmine interaction.
モニタリング
- Level of muscle relaxation
- Cardiac rate
- Respiratory rate
過量投与
* **Margin of Safety**: Reportedly 3 times the usual dose. * **Clinical Signs**: Apneustic breathing, nystagmus, hypotension, and contradictory muscle rigidity are associated with toxic levels. * **Toxicity Reports**: In dogs receiving 415-830 mg/kg, signs included hypothermia, mild tremors, ataxia, and vomiting. In cats receiving 132 mg/kg, signs included lethargy and anorexia. * **Treatment**: No specific antidote is available. Treatment is entirely **supportive** until the drug is cleared to sub-toxic levels.
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。