胺碘酮
胺碘酮是一種強效、廣效的**第三類抗心律不整藥物**，主要用於治療嚴重且難治的心室與心上室性心律不整。 由於其複雜的藥代動力學特性及顯著的潛在毒性，通常僅在傳統且毒性較低的療法無效時才考慮使用。 **臨床要點：** * 在結構上，胺碘酮是一種含碘的苯駢呋喃衍生物。一顆 200 毫克的錠劑約含有 75 毫克的碘，這可能會影響甲狀腺功能。 * 它具有高度脂溶性，導致其在組織中廣泛分佈並蓄積於脂肪組織中，這也是其半衰期極長且變異性大的原因。 * 在獸醫學中，最常用於患有隱性擴張性心肌病 (DCM) 的杜賓犬，特別是出現快速寬泛心室性心搏過速或暈厥的病例。 * 由於不良反應（包括肝毒性與甲狀腺功能障礙）的風險較高，必須進行嚴格的監測。
作用機制: Amiodarone is uniquely versatile, possessing properties of all four Vaughan-Williams antiarrhythmic classes, though it is primarily classified as a **Class III** agent. * **Class III (Primary):** Blocks **potassium (K+) channels** → prolongs phase 3 repolarization, action-potential duration (APD), and the effective refractory period (ERP) in myocardial cells. * **Class I:** Blocks **fast sodium (Na+) channels** → slows conduction velocity. * **Class II:** Non-competitively blocks **beta-adrenergic receptors** → provides sympatholytic effects, reducing heart rate. * **Class IV:** Weakly blocks **calcium (Ca2+) channels** → slows AV node conduction and suppresses automaticity. It is metabolized in the liver to its active metabolite, **desethylamiodarone**, which also contributes significantly to its antiarrhythmic effects.
各物種劑量
- For atrial fibrillation or ventricular arrhythmias primarily in ambulatory patients · 8-10 mg/kg PO every 12 hours · PO · q12h · Use caution if patient has bradycardia, AV blocks, or thyroid disorders.
- For ventricular arrhythmias secondary to occult cardiomyopathy in Doberman pinschers · 10 mg/kg PO twice daily for one week and then 8 mg/kg PO once daily. After 6 months reduce to 5 mg/kg PO once daily. · PO · q12h then q24h · Long-term · For severe V-Tach, mexiletine is added at 5-8 mg/kg three times daily for one week. Once efficacy confirmed, patient weaned off mexiletine.
- For ventricular tachycardia when other first line drugs (Class I antiarrhythmics ± beta-blockers) are ineffective · 10 mg/kg PO q12h for one week and then 5 mg/kg PO q12h for maintenance. · PO · q12h · Long-term
- For SVTs or Vtach · 10-20 mg/kg PO once daily (q24h) loading for 5-7 days; 5-10 mg/kg PO once daily thereafter. · PO · q24h · Long-term
- Ventricular and supraventricular arrhythmias, atrial fibrillation, ventricular pre-excitation syndromes · Dose not specified in monograph · PO/IV · Not specified · Not specified · Use as an IV infusion for recent onset atrial fibrillation has variable efficacy for restoring sinus rhythm but a high frequency of severe adverse effects.
- For conversion of atrial fibrillation or ventricular tachycardia · 5 mg/kg/hr for one hour, followed by 0.83 mg/kg/hr for 23 hours and then 1.9 mg/kg/hour for the following 30 hours. · IV · CRI · Up to 54 hours · Infusion was discontinued when conversion occurred or when any side effects were noted. Regimen should be further adapted based upon PK/PD studies.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Hypersensitivity to amiodarone or iodine
- Severe sinus-node dysfunction
- Severe sinus bradycardia
- 2nd or 3rd degree AV block
- Bradycardial syncope
不良反應
- Vomiting
- Anorexia
- Hepatopathy (elevated liver enzymes, bilirubinemia)
- Bradycardia
- Neutropenia
- Thrombocytopenia
- Positive Coombs' test
- Corneal deposits
- Injection site pain (IV)
- Facial pruritus and hyperemia (IV)
- Hind limb weakness (horses)
- Diarrhea (horses)
藥物相互作用
- Warfarin (Anticoagulants) · Significantly increases serum levels and/or pharmacologic/toxic effects of the anticoagulant.
- Digoxin · Significantly increases serum levels and/or toxic effects of digoxin. · major
- Cyclosporine · Increases cyclosporine levels; may increase creatinine.
- Lidocaine · Significantly increases serum levels and/or toxic effects of lidocaine. · moderate
- Methotrexate · Significantly increases serum levels and/or toxic effects with prolonged amiodarone administration. · major
- Phenytoin · Significantly increases serum levels and/or toxic effects of phenytoin.
- Procainamide · Significantly increases serum levels and/or toxic effects of procainamide.
- Quinidine · Significantly increases serum levels and/or toxic effects of quinidine.
- Azole Antifungals (ketoconazole, itraconazole) · Additive effects on QTc interval; possible serious arrhythmias.
- Cisapride · Additive effects on QTc interval; possible serious arrhythmias.
- Disopyramide · Additive effects on QTc interval; possible serious arrhythmias.
- Dolasetron · Additive effects on QTc interval; possible serious arrhythmias.
監測
- ECG (for antiarrhythmic efficacy and proarrhythmic effects)
- Gastrointestinal signs (anorexia, vomiting)
- CBC (for neutropenia, thrombocytopenia)
- Serial liver enzymes and bilirubin (baseline and routine monitoring)
- Thyroid function tests
- Blood pressure
- Pulmonary radiographs (if clinical signs such as dyspnea or cough occur)
過量
Clinical overdosage experience is limited. **Expected Signs:** * Hypotension * Bradycardia * Cardiogenic shock * AV block * Hepatotoxicity **Treatment:** * Therapy is primarily **supportive**. * Bradycardia may be managed with a pacemaker or beta-1 agonists (e.g., isoproterenol). * Hypotension may be managed with positive inotropic agents or vasopressors. * *Note:* Neither amiodarone nor its active metabolite are dialyzable.
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