Carvedilol
Carvedilol is a unique, third-generation **non-selective beta-blocker** with **alpha-1 adrenergic blocking** properties. In veterinary medicine, it is primarily investigated as an adjunctive treatment for **canine dilated cardiomyopathy (DCM)** and chronic heart failure. * **Dual Action:** Unlike traditional beta-blockers (like atenolol), carvedilol provides additional vasodilatory effects, reducing cardiac afterload. * **Controversial Use:** Its use in veterinary cardiology remains controversial. While it has proven mortality benefits in human heart failure, studies in dogs have shown mixed results regarding its efficacy in improving neurohormonal activation or ventricular remodeling at standard doses. * **Clinical Pearl:** Carvedilol is a profound negative inotrope. It can precipitate acute decompensation in patients with advanced or highly symptomatic heart failure. It requires extremely cautious, slow up-titration and is best initiated in minimally symptomatic patients.
กลไกการออกฤทธิ์: 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.
ขนาดยาตามชนิดสัตว์
- 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.
ขนาดยาเป็นข้อมูลอ้างอิงทางคลินิกสำหรับสัตวแพทย์ผู้มีใบอนุญาต โปรดตรวจสอบกับฉลากล่าสุดและผู้ป่วยแต่ละรายเสมอ
วิธีการให้ยา
ข้อห้ามใช้
- 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
อาการไม่พึงประสงค์
- Inappetence
- Lassitude (lethargy/fatigue)
- Hypotension
- Decompensation of heart failure (if titrated too rapidly)
- Bronchospasm (reported in humans)
- Mild hepatocellular injury (rare)
อันตรกิริยาระหว่างยา
- 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
การติดตาม
- Clinical efficacy (improvement in heart failure signs)
- Adverse effects (lethargy, inappetence, hypotension, worsening heart failure)
- Plasma drug levels (Target: 50-100 nanograms/mL)
การได้รับยาเกินขนาด
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.
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