Diltiazem for Dogs: A Medication That Regulates Heart Rhythms and Blood Pressure

Diltiazem is a medication that is prescribed by veterinarians to dogs with heart disease. Specifically, diltiazem is used in dogs to lower abnormally fast heart rates and high blood pressure.

Here’s everything you need to know if your dog is prescribed diltiazem for their heart health.

Diltiazem for dogs at a glance

What is diltiazem for dogs and how does it work?

Diltiazem is part of a class of medications called calcium channel blockers. Calcium channel blockers like diltiazem block calcium from flowing into smooth muscle cells, including cardiovascular cells. This results in relaxation of the heart muscles, which slows the heart rate.

It also dilates (expands) blood vessels, which can help reduce high blood pressure. Diltiazem also slows the rate of electrical impulses that travel through the heart. This helps slow a dog’s heart rate.

Diltiazem is rapidly absorbed in the gastrointestinal tract after it is swallowed and is primarily metabolized by the liver.

What is diltiazem used for in dogs?

Diltiazem is a medication that is used to manage the symptoms of certain cardiovascular conditions. It’s used to lower blood pressure and abnormally fast heart rates in dogs. But it does not cure heart disease.

Diltiazem can also be used in veterinary hospitals to treat life-threatening cardiovascular problems in dogs, including:

• Atrial fibrillation (a life-threatening arrhythmia)

• Supraventricular tachycardia (a heart rate that is too fast)

• Pulmonary hypertension (a condition that makes it harder for the heart to pump blood to the lungs)

Diltiazem is indicated to treat only specific heart conditions. It is not appropriate for all types of heart disease in dogs, and it may make some heart issues worse. Give your dog diltiazem only if your veterinarian has prescribed it.

Diltiazem is not FDA approved for use in dogs. But diltiazem is prescribed “off-label” or “extra-label” safely by veterinarians to dogs with specific heart-related health conditions.

What is the diltiazem dosage for dogs?

Diltiazem is available in a few forms for dogs. They include:

• Tablets

• Extended-release capsules

• Compounded oral liquid

• Compounded chewable tablet

The standard dose of diltiazem (regular-release tablets) for dogs is 0.5 mg/kg to 1.5 mg/kg of body weight every 8 to 12 hours. The dosage may be different for your dog, depending on their heart condition and the form of diltiazem your dog is prescribed. Your veterinarian will determine the most appropriate dose of diltiazem for your dog.

The bioavailability of diltiazem is lower in dogs than in humans, which is why the dose of diltiazem that is prescribed for your dog is different from what would be prescribed to a human. Read all dosing instructions carefully, and follow your veterinarian’s prescribing instructions exactly to avoid negative side effects associated with an overdose.

The injectable form of diltiazem is typically used only in veterinary emergency settings to treat life-threatening heart arrhythmias.

What are the common side effects of diltiazem in dogs?

The most common side effects of diltiazem in dogs are vomiting, decreased appetite, and weight loss. Weight loss is more common after your dog has been on the medication for a few months.

These side effects are not serious, but if they continue to affect your dog’s well-being, ask your veterinarian for advice.

Diltiazem can be given with or without food. If your dog has an upset stomach or appetite changes, try giving diltiazem with a small meal or treat.

The medication also has a bitter taste for dogs, which can cause them to drool. Giving diltiazem with a treat may help reduce this issue.

What are the most serious risks of diltiazem for dogs?

The most serious side effects of diltiazem in dogs include:

• Low blood pressure

• Slow heart rate

• Weakness

• Tiredness

• Fainting

• Abnormal heart rhythms

• Agitation or unusual behavior

• Liver problems

If you notice any of these severe side effects, call your veterinarian or take your dog to an emergency clinic.

The safety of diltiazem has not been evaluated in pregnant or nursing dogs or dogs with liver or kidney disease. It should be used with caution in these animals as well as older or frail dogs or dogs with congestive heart failure.

If your dog is prescribed diltiazem, your veterinarian will likely run a metabolic blood test to ensure your dog’s liver and kidneys are healthy. In addition, your veterinarian will want to see your dog for rechecks, which can include a physical examination, lab work, or cardiovascular tests.

Be sure to follow all of your veterinarian’s instructions on rechecks to ensure that your dog is receiving a safe and effective dose of diltiazem.

Does diltiazem interact with other dog medications?

Diltiazem should not be used in dogs that already receive beta blocker medications, such as atenolol and propranolol. When used together, these medications may make your dog’s heart condition worse.

Other medications that can interact negatively with diltiazem include:

• Benzodiazepines, such as diazepam and alprazolam (Xanax)

• Buspirone

• Cimetidine (Tagamet) or any other antacid

• Cyclosporine

• Digoxin (Lanoxin)

• Quinidine

• Rifampin

Your veterinarian may need to change the doses of any other medications your dog is receiving or monitor them carefully for side effects.

Many other medications may also interact with diltiazem. So be sure to tell your veterinarian about medications and supplements that your dog takes before they are prescribed diltiazem.

What should you do if your dog misses a dose of diltiazem?

If you forget to give a dose of diltiazem to your dog, call your veterinarian or an emergency clinic for advice.

In general, it is very important that diltiazem is given exactly on schedule. Otherwise, it can interrupt your dog’s heart rhythms in a way that might have life-threatening effects.

If you get off-schedule, talk with your veterinarian before adjusting the dosage schedule for your dog.

Why trust our experts?

Written by:

Sarah J. Wooten, DVM, CVJ

Dr. Sarah Wooten, DVM, CVJ, is a well-known international influencer in the veterinary and animal healthcare spaces. She has 16 years of experience in private practice and more than 15 years experience in veterinary media work.

Edited by:

Renée Fabian, MA

Renée Fabian is the senior pet health editor at GoodRx. She’s worked for nearly 10 years as a journalist and editor across a wide range of health and well-being topics.

Reviewed by:

Ghanasyam Bey, DVM

Ghanasyam Bey, DVM, is from Cleveland, Ohio, and attended Princeton University for undergraduate studies. After a year of biology research at Duke University, he attended Ohio State College of Veterinary Medicine.

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