Metoprolol in Dogs & Cats
Generic: Metoprolol
Metoprolol is a selective beta-1 adrenergic antagonist used in veterinary medicine to manage heart rate, arrhythmias, and hypertension by blocking the effects of catecholamines on the heart.
This medication is intended for dogs and cats.
Overview
Metoprolol is a cardioselective beta-blocker that acts primarily on the beta-1 receptors of the heart muscle. In veterinary clinical practice, it is utilized as an antiarrhythmic agent to slow the heart rate and reduce myocardial oxygen demand. It is often employed as an alternative to Atenolol when managing tachyarrhythmias or specific feline cardiac conditions. By modulating the autonomic nervous system's influence on the heart, veterinarians can stabilize rhythm and reduce the stress placed on the cardiac muscle during periods of disease.
What It Treats
- Tachyarrhythmias: Abnormal rapid heart rhythms that require rate control.
- Hypertrophic Cardiomyopathy (HCM): Commonly used in cats to decrease heart rate and improve diastolic filling time.
- Systemic Hypertension: Used in some cases to lower blood pressure, though other agents are often preferred as first-line therapy.
- Thyrotoxicosis-induced heart disease: Used to manage secondary cardiac impacts caused by hyperthyroidism.
How It Works
Metoprolol functions by competitively blocking beta-1 adrenergic receptors located specifically in the heart tissue. Under normal conditions, these receptors respond to neurotransmitters like adrenaline, which increase heart rate and the strength of heart contractions. By blocking these receptors, metoprolol effectively 'calms' the heart, slowing the heart rate and reducing the cardiac workload. Because it is 'cardioselective,' it has a higher affinity for heart receptors compared to beta-2 receptors found in the lungs, making it safer for patients with certain respiratory sensitivities compared to non-selective beta-blockers.
Dosage
Dosage is highly variable based on the patient's condition, species, and weight. It is imperative that you follow the exact dosing schedule provided by your veterinarian. Never adjust the dose or frequency without professional guidance, as sudden changes can cause dangerous heart rhythm disturbances or acute heart failure.
Administration
Metoprolol is typically administered orally as a tablet. It can be given with or without food, though consistency is key to maintaining stable blood levels. If your pet misses a dose, do not double the dose; continue with the next scheduled administration. If your pet struggles with oral medication, discuss compounding options or alternative delivery methods with your veterinarian.
Storage
Store metoprolol in a tightly sealed container at room temperature, ideally between 68°F and 77°F (20°C to 25°C). Keep the medication protected from moisture, light, and high heat. Ensure it is stored well out of the reach of children and pets to prevent accidental ingestion.
Contraindications
Metoprolol should not be used in patients with decompensated heart failure, as the negative inotropic effects can worsen the condition and lead to cardiogenic shock. It is also contraindicated in patients with second- or third-degree heart block, severe bradycardia, or sick sinus syndrome, as further slowing the heart rate can be fatal. Caution is advised in patients with diabetes mellitus, as beta-blockers can mask the clinical signs of hypoglycemia.
Interactions
Metoprolol may interact with other cardiac medications, such as [Digoxin](/medications/digoxin-in-dogs-and-cats), potentially leading to excessive slowing of the heart rate. Combining it with calcium channel blockers like diltiazem can also result in profound bradycardia or cardiac arrest. When used alongside ACE inhibitors like [Enalapril](/medications/enalapril-in-dogs-and-cats), blood pressure must be closely monitored to prevent symptomatic hypotension. Always inform your veterinarian of all supplements and medications currently in use.
Side Effects
- Bradycardia (excessively slow heart rate)
- Hypotension (low blood pressure)
- Lethargy or general weakness
- Exercise intolerance
- Congestive heart failure exacerbation
- Depression of myocardial contractility
Sources & References
Frequently Asked Questions
This information is educational only and not a substitute for professional veterinary advice. Always consult a licensed veterinarian before starting or changing any medication.