Metoprolol

What is metoprolol?

Metoprolol is a beta-blocker used to treat certain heart rhythm problems and hypertension (high blood pressure) in cats and dogs. It has also been used in the treatment of hypertrophic cardiomyopathy (HCM) in cats.

It is used off label (extra label) in veterinary medicine. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet metoprolol?

• Metoprolol comes in tablet form. Tablets may be compounded into liquid form.
• Tablets are given orally (by mouth).
• Measure liquid medications carefully. Contact your veterinarian if you have trouble measuring or giving the medication.
• This medication may be given with or without food.
• If your pet vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian.
• Give this medication to your pet for the entire time prescribed by your veterinarian, even if it appears that your pet is feeling better.

This medication should take effect within 1 to 2 hours, though effects will not be noticed outwardly.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then wait the recommended amount of time for the next dose, as prescribed by your veterinarian. Do not give the pet two doses at once.

Are there any potential side effects?

Metoprolol may cause the following side effects:

• Decreased energy
• Diarrhea

Serious adverse reactions may occur. If any of the following signs develop, stop giving metoprolol and contact your veterinarian immediately:

• An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face
• Collapse, weakness
• Very slow heart rate
• Coughing, wheezing, trouble breathing

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses, but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment and notify your veterinarian if you have any concerns. 

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, though effects may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

DO NOT USE metoprolol in:

• Pets with severe heart failure, heart block, or very slow heart rate
• Pets with asthma
• Pets that are in shock
• Pets that are allergic to any component of the medication or who are allergic to similar drugs (e.g., propranolol, sotalol)

USE WITH CAUTION in:

• Pets with liver disease
• Pets with diabetes mellitus
• Pets with hyperthyroidism

Are there any drug interactions I should be aware of?

Several medications should be USED WITH CAUTION when given with metoprolol, including:

• Antidiabetic agents (e.g., insulin)
• Calcium channel blockers (e.g., amlodipine)
• Ciuretics (e.g., furosemide)
• Hydralazine
• Lidocaine
• Methimazole
• Nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., meloxicam)
• Phenobarbital

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Your veterinarian will assess baseline heart function (e.g., rate, rhythm, ECG, blood pressure) before starting this medication and periodically throughout treatment.
• Your veterinarian will schedule follow-up visits for monitoring. In this case, follow your veterinarian’s directions.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian. 

How do I store metoprolol?

• Store at room temperature in a tight container.
• Store compounded forms of this medication according to the label.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms. Report any adverse effects to the FDA or Health Canada.