美西律
Mexiletine
Mexiletine hydrochloride
別名: Mexilen · Mexitilen · Myovek · Ritalmex · Ko-1173 · mexiletini hydrochloridum
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
各物種劑量
🌎 NA — North America🌍 EU — Europe
狗
| 適應症 | 劑量 | 途徑 | 頻次 | 療程 | 地區 |
|---|---|---|---|---|---|
| Treating or assisting in treatment of ventricular arrhythmias | 5-8 mg/kg | PO | q8h | — | 🌎 NA |
| Treating or assisting in treatment of ventricular arrhythmias | 4-10 mg/kg | PO | q8h | — | 🌎 NA |
| Ventricular arrhythmias in Boxers | 5-7.5 mg/kg | PO | three times daily | — | 🌎 NA |
| Treating or assisting in treatment of ventricular arrhythmias | 4-8 mg/kg | PO | q8h | — | 🌎 NA |
| Familial arrhythmic cardiomyopathy of Boxers (ARVC) | 5-8 mg/kg | PO | q8h | — | 🌎 NA |
| Treating or assisting in treatment of ventricular arrhythmias | 5-6 mg/kg | PO | q8h | — | 🌎 NA |
| Myotonia congenita or myokymia | 8.3 mg/kg | PO | q8h | — | 🌎 NA |
- Ventricular arrhythmias in Boxers: Given with sotalol at 1.5-3 mg/kg twice daily; was successful in 7/8 dogs treated in study.
- Treating or assisting in treatment of ventricular arrhythmias: Combined with atenolol (0.5 mg/kg PO q12-24h).
- Familial arrhythmic cardiomyopathy of Boxers (ARVC): Given with atenolol at 12.5 mg (total dose) q12h.
- Treating or assisting in treatment of ventricular arrhythmias: Always give with food to avoid nausea.
- Myotonia congenita or myokymia: Most studied in Chow Chows, miniature schnauzers, and Jack Russell terriers.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新仿單及個別病患確認。
概覽
美西律（Mexiletine）是一種口服的 IB類抗心律不整藥物，其電生理特性與利多卡因（Lidocaine）非常相似。由於利多卡因具有顯著的首過代謝效應且無法口服，美西律常被視為用於長期控制心律不整的「口服版利多卡因」。
在獸醫學中，它主要用於治療犬隻的心室性心律不整（如心室提早收縮 PVCs 和心室性心搏過速）。它特別常用於患有致心律不整性右心室心肌病（ARVC）的拳師犬，以及患有擴張性心肌病（DCM）的杜賓犬。臨床上常與乙型交感神經阻斷劑（如 Atenolol）或 Sotalol 併用以達到協同效果。
此外，美西律也可用於治療某些罕見的遺傳性肌肉疾病，包括先天性肌強直（常見於鬆獅犬和迷你雪納瑞）及肌纖維顫搐（常見於傑克羅素㹴）。
作用機轉
Mexiletine is a Class IB antiarrhythmic.
- Mechanism: It binds to and inhibits the inward fast sodium channels (Na+) in the myocardial cell membrane.
- Electrophysiologic Effects: By blocking these channels, it reduces the rate of rise of the action potential (Phase 0). In Purkinje fibers, it decreases automaticity, shortens the action potential duration, and decreases the effective refractory period.
- Selectivity: Like lidocaine, it is highly selective for diseased, ischemic, or rapidly firing myocardial tissue, making it effective at suppressing ventricular ectopic pacemakers without significantly depressing normal sinus node function or conduction (unless pre-existing abnormalities exist).
安全性與警告
禁忌症
- Pre-existing 2nd or 3rd degree AV block (without a pacemaker)
- Cardiogenic shock
- Known hypersensitivity to mexiletine
不良反應
- Vomiting (very common)
- Nausea
- Trembling/Tremors
- Unsteadiness/Ataxia
- Dizziness
- Depression/Lethargy
- Shortness of breath
- Proarrhythmia (PVCs)
- Chest pain
- Seizures (rare)
- Agranulocytosis (rare)
- Thrombocytopenia (rare)
注意事項
Use with extreme caution in patients with severe congestive heart failure, acute myocardial infarction, hepatic function impairment, hypotension, intraventricular conduction abnormalities, sinus node function impairment, or a pre-existing seizure disorder.
Clinical Note: Mexiletine is secreted into maternal milk; use of a milk replacer is recommended if the nursing mother is receiving the drug. FDA Pregnancy Category C.
藥物交互作用
May slow the absorption of mexiletine.
May reduce the rate of oral absorption.
May increase or decrease mexiletine blood levels.
May accelerate the metabolism of mexiletine.
May cause additive adverse effects (especially CNS toxicity).
May accelerate the absorption of mexiletine.
May slow the absorption of mexiletine.
May accelerate the metabolism of mexiletine.
May accelerate the metabolism of mexiletine.
May accelerate the metabolism of mexiletine.
May accelerate the metabolism of mexiletine.
Mexiletine may reduce the metabolism of theophylline, potentially leading to theophylline toxicity.
May accelerate the renal excretion of mexiletine.
May reduce the urinary excretion of mexiletine.
監測
- Electrocardiogram (ECG) to assess antiarrhythmic efficacy and monitor for proarrhythmia
- Clinical signs of adverse effects (especially GI and CNS signs)
- Plasma concentrations (Therapeutic range in humans: 0.5-2 mcg/mL; note that toxicity may be noted even at therapeutic levels)
- Liver enzymes (AST may transiently increase in a small percentage of patients)
藥物動力學
吸收
Relatively well absorbed from the gastrointestinal tract with a low first-pass effect.
分佈
Moderately bound to plasma proteins (60-75% in humans).
代謝
Metabolized in the liver to inactive metabolites.
排除
Excreted via the kidneys. Renal excretion rate is dependent on urinary pH (acidification accelerates excretion, alkalinization reduces it).
過量
Toxicity associated with overdosage can be significant and life-threatening.
- Clinical Signs: In human case reports, CNS signs (tremors, seizures, depression) always preceded cardiovascular signs (hypotension, bradycardia, heart block).
- Treatment:
- Perform GI tract emptying protocols (emesis/gastric lavage) if indicated and safe.
- Administer supportive therapy.
- Acidification of the urine may be considered to enhance urinary excretion.
- Atropine may be useful if severe hypotension or bradycardia occurs.
可用產品
劑型
- Oral Capsules: 150 mg, 200 mg, 250 mg
人用標示
- Mexiletine Oral Capsules: 150 mg, 200 mg & 250 mg (generic)
各地核准狀態
暫無法規資料: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Mexiletine capsules should be stored in tight containers at room temperature.
飼主須知
- 務必隨餐餵食：此藥物極易引起胃部不適、噁心和嘔吐。與豐盛的食物一起服用可大幅降低此風險。
- 嚴格遵守給藥時間：請務必按照獸醫師指示給藥，切勿自行跳過劑量或停藥。心室性心律不整可能危及生命，若中斷藥物，心律不整可能會迅速復發。
- 觀察副作用：如果您的寵物出現持續嘔吐、顫抖、步態不穩、頭暈、極度疲倦或呼吸急促，請立即聯繫您的獸醫師。
VetSheet 藥物參考供合格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商最新仿單。