カルベジロール
カルベジロールは、**α1アドレナリン受容体遮断**作用を併せ持つユニークな第3世代の**非選択的β遮断薬**です。獣医療においては、主に**犬の拡張型心筋症（DCM）**および慢性心不全の補助療法として研究されています。 * **二重作用：** 従来のβ遮断薬（アテノロールなど）とは異なり、カルベジロールは追加の血管拡張作用をもたらし、心臓の後負荷を軽減します。 * **使用に関する議論：** 獣医循環器学における使用は依然として議論の余地があります。ヒトの心不全では死亡率低下の利点が証明されていますが、犬の研究では、標準用量での神経体液性活性化や心室リモデリングの改善に関する有効性はまちまちです。 * **臨床上のポイント：** カルベジロールは強力な陰性変力作用を持ちます。進行した、あるいは症状の重い心不全患者において急性代償不全を引き起こす可能性があります。極めて慎重かつゆっくりとした用量漸増が必要であり、症状が軽微な患者から開始するのが最適です。
作用機序: Carvedilol exerts its cardiovascular effects through multiple mechanisms: * **Non-selective Beta-Adrenergic Blockade (β1 and β2):** Heart failure leads to chronic sympathetic nervous system (SNS) activation → tachycardia, renin-angiotensin-aldosterone system (RAAS) activation, beta-receptor downregulation, and myocyte necrosis. Carvedilol blocks these receptors → **reverses/diminishes SNS toxicity**, reduces heart rate, and decreases myocardial oxygen demand. * **Selective Alpha-1 Adrenergic Blockade:** Blocks peripheral α1-receptors → **vasodilation** → reduces systemic vascular resistance and cardiac afterload. * **Antioxidant Properties:** Carvedilol and its metabolites act as potent scavengers of reactive oxygen species (ROS) and inhibit lipid peroxidation, protecting the myocardium from oxidative stress. * **Antidysrhythmic Effects:** Secondary to its beta-blocking and membrane-stabilizing properties.
動物種別の用量
- Heart failure (adjunctive therapy) · ¼-½ of a 3.125 mg tablet PO twice daily · PO · twice daily · Usual starting dose. Start at the low end of the dosing range and gradually titrate upward carefully watching to avoid negative inotropic effects.
- Early/mild heart failure or later stages of CHF · 0.2 mg/kg PO twice daily initially with slow titration upwards towards a dose of 0.8 mg/kg twice daily · PO · twice daily · Beta blockers are best employed in dogs that are minimally symptomatic. Many dogs with CHF will not tolerate this upward titration.
- Heart failure (target plasma concentration) · 0.5 mg/kg PO twice daily · PO · twice daily · Should result in beta-blockade, but maximum beta-blockade may require doses of >0.7-0.9 mg/kg. Because of bioavailability variations, plasma monitoring, clinical trials and uptitration protocols may be beneficial.
- Dilated cardiomyopathy · 0.3 mg/kg PO q12h · PO · q12h · 3 months · Did not produce any significant improvements in neurohormonal activation, heart size, or owner-perceived quality of life. Doses >0.3 mg/kg q12h are likely to be required to effect changes in ventricular remodeling and function.
- Chronic heart failure / Dilated Cardiomyopathy (DCM) · Start at 0.05-0.1 mg/kg, gradually increase at 2-week intervals to target dose of 0.3-0.4 mg/kg · PO · q12h · Long-term · Increase dose only if tolerated.
- ACVIM stage B2 degenerative mitral valve disease · 0.3 mg/kg, increased at intervals up to 1.1 mg/kg · PO · q12h · Long-term · For cardiac remodelling with no signs of cardiac failure.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Class IV decompensated heart failure
- Bronchial asthma
- 2nd or 3rd degree AV block
- Sick sinus syndrome (unless artificially paced)
- Severe bradycardia
- Cardiogenic shock
- Hypersensitivity to the drug
有害事象
- Inappetence
- Lassitude (lethargy/fatigue)
- Hypotension
- Decompensation of heart failure (if titrated too rapidly)
- Bronchospasm (reported in humans)
- Mild hepatocellular injury (rare)
薬物相互作用
- Beta-Blockers (other) · Use with carvedilol may cause additive effects
- Calcium Channel Blockers (e.g., diltiazem, verapamil) · May rarely cause hemodynamic compromise
- Cimetidine · May decrease metabolism and increase AUC of carvedilol
- Clonidine · Carvedilol may potentiate the cardiovascular effects of clonidine
- Cyclosporine · Carvedilol may increase cyclosporine levels
- Digoxin · Can increase digoxin plasma concentrations by approximately 15% · major
- Fluoxetine, Paroxetine, Quinidine · May increase R(+)carvedilol concentrations and increase alpha-1 blocking effects (vasodilation)
- Insulin / Oral Antidiabetic Agents · Carvedilol may enhance the blood glucose lowering effects of insulin or other antidiabetic agents
- Rifampin · Can decrease carvedilol plasma concentrations by as much as 70% · moderate
- Reserpine · Can cause increased bradycardia and hypotension in patients taking carvedilol
- Anaesthetic agents · Enhanced hypotensive effect and myocardial depression · major
- Phenothiazines · Enhanced hypotensive effect · moderate
モニタリング
- Clinical efficacy (improvement in heart failure signs)
- Adverse effects (lethargy, inappetence, hypotension, worsening heart failure)
- Plasma drug levels (Target: 50-100 nanograms/mL)
過量投与
The acute oral LD50 in healthy rats and mice is greater than 8 grams/kg. **Clinical Signs of Overdose:** * Severe hypotension * Cardiac insufficiency * Bradycardia * Cardiogenic shock * Death due to cardiac arrest **Treatment:** * Gut emptying protocols should be considered if ingestion was recent. * **Bradycardia:** Treat with atropine. * **Cardiovascular Support:** Support function with glucagon and sympathomimetics (e.g., dobutamine, epinephrine). * Contact an animal poison control center for specific information.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。