メトプロロール
Metoprolol
Metoprolol tartrate, Metoprolol succinate
別名: Lopressor · Toprol XL · CGP-2175E · H-93/26
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 |
|---|---|---|---|---|---|
| For rate control in chronic atrial fibrillation | 0.25-1 mg/kg PO q1224h. | PO | q1224h | — | 🌎 NA |
| For CHF (early/mild or well-controlled) | 0.2 mg/kg PO twice daily, with slow titration upwards every 2-3 weeks up to 0.4-6.6 mg/kg PO three times a day. | PO | BID to TID | — | 🌎 NA |
| To decrease the incidence of atrial fibrillation and flutter in dogs undergoing valve surgery | 0.4-1 mg/kg PO q24h | PO | q24h | — | 🌎 NA |
- For rate control in chronic atrial fibrillation: Note: 'q1224h' is transcribed exactly as it appears in the source text, likely a typo for q12-24h.
- For CHF (early/mild or well-controlled): Many dogs will not tolerate this upward titration.
- To decrease the incidence of atrial fibrillation and flutter in dogs undergoing valve surgery: Using sustained release metoprolol (ToprolXR) administered before and as soon as feasible after surgery.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| As an oral beta blocker | 2-15 mg (total dose) PO q8h | PO | q8h | — | 🌎 NA |
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
メトプロロールは、心臓選択性（β1特異的）アドレナリン受容体遮断薬であり、獣医学において様々な心血管疾患の管理に広く使用されています。
主な臨床応用は以下の通りです：
- 上室性頻脈性不整脈および心室性期外収縮（PVC/VPC）の管理。
- 全身性高血圧の治療。
- 猫の肥大型心筋症（HCM）の治療（動的左室流出路狭窄を軽減し、拡張期充満時間を改善します）。
相対的なβ1選択性を持つため、気管支収縮性疾患（猫喘息など）を併発している患者において、非選択性β遮断薬（プロプラノロールなど）よりも一般的に安全と考えられていますが、高用量では選択性が失われる可能性があるため注意が必要です。
作用機序
Metoprolol competitively blocks beta1-adrenergic receptors located primarily in the myocardium.
Mechanism Pathway: Blockade of beta1-receptors → decreased activation of adenylyl cyclase → reduced intracellular cAMP → decreased intracellular calcium influx.
This results in:
- Negative chronotropy: Decreased sinus heart rate.
- Negative dromotropy: Slowed atrioventricular (AV) conduction.
- Negative inotropy: Decreased myocardial contractility and cardiac output.
- Decreased myocardial oxygen demand and reduced blood pressure.
Clinical Pearl: Metoprolol lacks intrinsic sympathomimetic activity (ISA) and membrane-stabilizing activity. At higher dosages, its cardioselectivity diminishes, leading to beta2-receptor blockade in bronchial smooth muscle → potential bronchoconstriction.
安全性・警告
禁忌
- Overt or unstable heart failure
- Hypersensitivity to beta-blockers
- Greater than first-degree heart block
- Sinus bradycardia
有害事象
- Bradycardia
- Lethargy and depression
- Impaired AV conduction
- Congestive heart failure (CHF) or worsening of heart failure
- Hypotension
- Hypoglycemia
- Bronchoconstriction (at high doses)
- Syncope
- Diarrhea
注意事項
Withdrawal Warning: Do not abruptly discontinue metoprolol therapy in chronic users. Abrupt cessation can lead to rebound tachycardia and exacerbation of clinical signs; taper the dose gradually.
- Respiratory Disease: Use with caution in patients with bronchospastic lung disease, even though it is relatively beta1-selective.
- Hepatic Impairment: Use cautiously in patients with significant hepatic insufficiency due to extensive hepatic metabolism.
- Endocrine: Can mask clinical signs of hypoglycemia and thyrotoxicosis. Use cautiously in labile diabetic patients as it can cause hypoglycemia or hyperglycemia.
- Cardiac: Use cautiously in patients with sinus node dysfunction or compensated CHF.
医薬品相互作用
Increased risk for heart failure and hypotension due to additive myocardial depressant effects.
Concurrent use should be done with caution; additive negative inotropic and chronotropic effects, particularly in patients with preexisting cardiomyopathy or CHF.
May increase negative effects on SA or AV node conduction.
May increase the hypotensive effect of metoprolol.
May increase the risks for pulmonary hypertension in uremic patients.
May increase metoprolol plasma concentrations.
Potential for additive effects including hypotension and bradycardia.
May increase metoprolol plasma concentrations.
May have their actions blocked by metoprolol, and they may in turn reduce the efficacy of the beta-blocker.
監視
- Cardiac function
- Pulse rate
- ECG (if necessary)
- Blood pressure (if indicated)
- Signs of toxicity (bradycardia, hypotension, lethargy)
薬物動態
半減期
吸収
Rapidly and nearly completely absorbed from the GI tract, but undergoes a high first-pass effect (50%), reducing systemic bioavailability.
分布
Very low protein binding (5-15%). Distributes well into most tissues. Crosses the blood-brain barrier (CSF levels are ~78% of serum levels). Crosses the placenta, and milk concentrations are 3-4 times higher than plasma.
代謝
Primarily biotransformed in the liver.
消失
Unchanged drug and metabolites are principally excreted in the urine.
過剰投与
Overdosage primarily results in extensions of the drug's pharmacologic effects: hypotension, bradycardia, bronchospasm, cardiac failure, and potentially hypoglycemia.
Treatment:
- Decontamination: If recent oral ingestion, consider emptying the gut and administering activated charcoal. Caution: Inducing emesis can be risky as coma and seizures may develop rapidly.
- Monitoring: Continuous ECG, blood pressure, blood glucose, and potassium.
- Cardiovascular Support: Treat symptomatically. Use IV fluids and pressor agents for hypotension.
- Bradycardia: Treat with atropine. If atropine fails, isoproterenol may be given cautiously. A transvenous pacemaker may be necessary.
- Cardiac Failure: May be treated with digitalis glycosides, diuretics, and oxygen.
- Antidote: Glucagon (5-10 mg IV - human dose) may increase heart rate and blood pressure and reduce the cardiodepressant effects of metoprolol.
製品
製剤
- Oral tablets (tartrate)
- Extended-release oral tablets (succinate)
- Injection (tartrate)
- Compounded oral suspension
ヒト用医薬品
- Metoprolol Tartrate Oral Tablets: 25 mg, 50 mg & 100 mg (Lopressor, generic)
- Metoprolol Succinate Extended-Release Tablets: 25 mg, 50 mg, 100 mg & 200 mg (Toprol XL, generic)
- Metoprolol Tartrate Injection: 1 mg/mL in 5 mL amps and Carpuject sterile cartridge units (Lopressor, 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
Store all products protected from light. Store tablets in tight, light-resistant containers at room temperature. Avoid freezing the injection. Compounded oral suspensions (10 mg/mL) retain >95% potency for 60 days when stored at 4°C or 25°C and protected from light.
飼主向け情報
飼い主様への重要な情報
- 規則正しい投薬が重要です：効果を得るためには、獣医師の指示通りにすべての用量を正確に投与する必要があります。
- 急に服用を中止しないでください：獣医師に相談することなく、突然投薬を中止しないでください。心拍数が危険なレベルまで上昇したり、心疾患が悪化する恐れがあります。
- 注意すべき症状：ペットが異常に元気がない、運動を嫌がる、息切れや咳をする、または行動や態度に急な変化が見られた場合は、直ちに獣医師にご連絡ください。
- 糖尿病のペット：ペットが糖尿病を患っている場合、この薬が低血糖の通常のサインを隠してしまう可能性があるため、血糖値を注意深く監視してください。
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。