癒創甘油醚 (Guaifenesin)
**癒創甘油醚**（Guaifenesin，又稱 glyceryl guaiacolate 或 GG）是一種具有雙重用途的藥物。在獸醫學中，它主要作為**注射用肌肉鬆弛劑**，用於大型動物短時間麻醉（30-60分鐘）時，促進平穩無興奮的麻醉誘導與恢復。 * **麻醉輔助**：提供骨骼肌鬆弛，且不影響橫膈膜功能。 * **口服祛痰劑**：在人類與獸醫學中用於稀釋黏液以控制呼吸道疾病，儘管其臨床療效的確切證據仍有爭議。 **臨床要點**：癒創甘油醚本身並非麻醉劑；它能增強麻醉前給藥與麻醉劑的作用，必須在平衡麻醉方案（例如「三重滴注」或 GKX）中使用。它具有輕微的內在鎮痛與鎮靜特性。
作用機制: * **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.
各物種劑量
- 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%.
給藥途徑
禁忌症
- Concurrent use with physostigmine
- Concentrations greater than 5% in ruminants (due to hemolysis risk)
不良反應
- Mild hypotensive effect
- Increase in cardiac rate
- Thrombophlebitis (IV administration)
- Perivascular tissue reaction
- Hemolysis (especially in ruminants with >5% solutions)
- Increased gastrointestinal motility
藥物相互作用
- 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.
監測
- Level of muscle relaxation
- Cardiac rate
- Respiratory rate
過量
* **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.
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