瑞芬太尼
**瑞芬太尼 (Remifentanil)** 是一種強效、超短效的合成**mu-鴉片類促效劑**，結構上與芬太尼相似。在獸醫學中，它主要作為全身麻醉期間的鎮痛輔助劑，特別適用於全靜脈麻醉 (TIVA) 方案。 主要藥理特點包括： * **非器官依賴性代謝**：與大多數依賴肝臟代謝和腎臟排泄的鴉片類藥物不同，瑞芬太尼會被血漿、紅血球和組織中的非特異性酯酶迅速降解。這使其對患有嚴重肝腎功能不全的病患極為安全。 * **作用消退迅速**：其極短的作用時間使得無論輸注時間多長，病患都能快速且可預測地甦醒，減少了其他鴉片類藥物常見的長時間鎮靜副作用。 * **天花板效應**：與其他作為麻醉輔助劑的鴉片類藥物一樣，它具有天花板效應，即增加劑量不會進一步增強鎮痛效果，但可能會增加不良反應。 > **臨床要點**：由於停止輸注後瑞芬太尼不會提供任何殘留的術後鎮痛效果，因此在停止輸注前，必須給予長效鎮痛藥（如 NSAIDs、丁丙諾啡或局部神經阻斷），以防止急性甦醒期譫妄和疼痛。
作用機制: Remifentanil acts as a selective agonist at **mu-opioid receptors** (G-protein coupled receptors) located primarily in the pain-regulating areas of the central nervous system (limbic system, spinal cord, thalamus, midbrain). **Mechanism Pathway**: Remifentanil binds to **mu-receptors** → inhibits adenylate cyclase → decreases intracellular cAMP → promotes opening of potassium channels and inhibits voltage-gated calcium channels → hyperpolarization of nociceptive neurons → suppression of substance P release and profound analgesia. **Metabolism**: It is rapidly metabolized via hydrolysis of its propanoic acid-methyl ester linkage by **nonspecific blood and tissue esterases** (not plasma pseudocholinesterase). The principal carboxylic acid metabolite (GR90291) is virtually inactive (4000 times less potent in dogs).
各物種劑量
- Analgesic adjunct to general anesthesia · 0.2 micrograms/kg/minute (for OHE) to 0.3 micrograms/kg/minute (to reduce stimulus-induced movement) · IV · CRI · In propofol-anesthetized (0.3 mcg/kg/min) cats.
- Analgesic adjunct to general anesthesia · 4 micrograms/kg bolus IV, followed by 6-20 micrograms/kg/hr CRI. · IV · CRI · Do not confuse mcg/kg/hr with mcg/kg/min.
- Analgesic adjunct to general anesthesia · 1 microgram/kg IV loading dose slowly over 2-3 minutes, followed by a 0.1-0.2 microgram/kg/minute CRI. · IV · CRI · Do not confuse mcg/kg/hr with mcg/kg/min.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to remifentanil or other fentanyl analogs
- Epidural or intrathecal administration (contraindicated due to the presence of glycine in the formulation)
不良反應
- Respiratory depression
- Apnea
- Bradyarrhythmias
- Hypotension
- Hyperthermia (noted in cats)
- Anaphylaxis (rare)
藥物相互作用
- CNS Depressants (e.g., propofol, isoflurane, thiopental) · Additive CNS and respiratory depression; remifentanil significantly reduces MAC and induction agent requirements.
- Diuretics · Opiates may decrease diuretic efficacy in patients with congestive heart failure.
- Monoamine Oxidase Inhibitors (e.g., amitraz, selegiline) · Severe and unpredictable opiate potentiation may occur; use is generally not recommended if an MAOI has been used within 14 days.
- Skeletal Muscle Relaxants · Remifentanil may enhance neuromuscular blockade.
- Nitrous Oxide · High doses of remifentanil combined with nitrous oxide may cause cardiovascular depression.
- Tricyclic Antidepressants (e.g., clomipramine, amitriptyline) · May exacerbate the effects of tricyclic antidepressants.
- Warfarin · Opiates may potentiate anticoagulant activity.
監測
- Cardiac rate and rhythm (ECG)
- Respiratory rate and depth / Capnography (ETCO2)
- Pulse oximetry (SpO2) or arterial blood gas
- Blood pressure (direct or indirect)
- Body temperature (especially in cats)
過量
Overdosage manifests as an enhancement of the drug's pharmacological effects. **Clinical Signs**: * Apnea and severe respiratory depression * Chest-wall rigidity * Hypoxemia * Hypotension and severe bradycardia * Seizures **Treatment**: 1. **Discontinue drug administration immediately.** 2. Provide supportive therapy, primarily **mechanical ventilation** and oxygen administration. Because the drug is cleared so rapidly by tissue esterases, this is often the only intervention required. 3. Administer IV fluids, and use **glycopyrrolate or atropine** to manage bradycardia or hypotension. 4. **Naloxone** may be used to reverse mu-opioid activity, but caution is advised as it can lead to acute pain and sympathetic hyperactivity.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。