メキシレチン
Mexiletine
Mexiletine hydrochloride
別名: Mexilen · Mexitilen · Myovek · Ritalmex · Ko-1173 · mexiletini hydrochloridum
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| 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.
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
メキシレチンは、リドカインと非常に似た電気生理学的特性を持つ経口のクラスIB抗不整脈薬です。リドカインは初回通過効果が大きく経口投与できないため、メキシレチンは不整脈の慢性管理における「経口版リドカイン」としてよく利用されます。
獣医療では主に、犬の心室性不整脈（心室期外収縮［PVC］や心室頻拍など）の治療に使用されます。特に、不整脈源性右室心筋症（ARVC）のボクサーや、拡張型心筋症（DCM）のドーベルマンでの使用が顕著です。相乗効果を得るために、β遮断薬（アテノロールなど）やソタロールと併用されることがよくあります。
さらに、メキシレチンは、先天性ミオトニー（チャウチャウやミニチュア・シュナウザーに見られる）やミオキミア（ジャック・ラッセル・テリアに見られる）などの特定のまれな遺伝性筋疾患の治療にも利用されます。
作用機序
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・警告
禁忌
- Pre-existing 2nd or 3rd degree AV block (without a pacemaker)
- Cardiogenic shock
- Known hypersensitivity to mexiletine
有害事象
- 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.
医薬品相互作用
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.
監視
- 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)
薬物動態
吸収
Relatively well absorbed from the gastrointestinal tract with a low first-pass effect.
分布
Moderately bound to plasma proteins (60-75% in humans).
代謝
Metabolized in the liver to inactive metabolites.
消失
Excreted via the kidneys. Renal excretion rate is dependent on urinary pH (acidification accelerates excretion, alkalinization reduces it).
過剰投与
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.
製品
製剤
- Oral Capsules: 150 mg, 200 mg, 250 mg
ヒト用医薬品
- Mexiletine Oral Capsules: 150 mg, 200 mg & 250 mg (generic)
規制ステータス
規制データなし: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Mexiletine capsules should be stored in tight containers at room temperature.
飼主向け情報
- 必ず食事と一緒に与えてください：この薬は胃の不快感、吐き気、嘔吐を頻繁に引き起こします。十分な食事と一緒に与えることで、このリスクを大幅に減らすことができます。
- 指示通りの投薬が重要です：獣医師に相談せずに、薬を飛ばしたり中止したりしないでください。心室性不整脈は生命を脅かす可能性があり、薬を中断すると急速に再発する恐れがあります。
- 副作用の観察：ペットに持続的な嘔吐、震え、ふらつき、めまい、極度の無気力、または呼吸促迫が見られた場合は、すぐに獣医師にご連絡ください。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。