Diltiazem for Dogs

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Diltiazem Used for in Dogs?

Diltiazem is a type of medication called a calcium channel blocker that’s used to treat certain arrhythmias (abnormal or irregular heartbeats). Diltiazem is primarily used in arrhythmias with a fast heart rate (tachycardia) such as supraventricular tachycardia (SVT). Diltiazem can also be used to treat hypertension (high blood pressure) in dogs and cats.

Diltiazem can be used as a maintenance medication given by mouth as well as given intravenously (IV) in the hospital for pets with heart-related emergencies. 

Giving diltiazem with certain medications can result in health risks to your pet; so it’s important to discuss your pet’s medications, including vitamins and supplements, and medical conditions with your veterinarian.

While Diltiazem is a generic drug, FDA-approved for human use under several brand names, including Cardizem® and Tiazac®, diltiazem is not currently FDA-approved as a veterinary medication. It is, however, readily utilized in the veterinary field, and veterinarians can legally prescribe certain human drugs for use in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label.

In certain circumstances, your vet may recommend a compounded formulation of diltiazem.

Compounded medications are prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form, the dosage strength is not commercially available, or the pet is allergic to an ingredient in the FDA-approved medication. Compounded medications are not FDA-approved. They’re created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs.

Ultimately, your veterinarian will determine whether this medication is right for your pet.

How Diltiazem Works in Dogs

Diltiazem is a calcium channel blocker, which means it blocks calcium ions from entering the cells of the heart and blood vessels. This causes the heart rate to slow and blood vessels to relax and dilate, which lowers blood pressure because blood can then flow more easily.

Diltiazem can slow abnormally fast heartbeats in certain arrhythmias such as SVT due to its ability to slow down the electrical signals in the muscles of the heart that are responsible for its contraction.

Diltiazem should not be used with pets that have certain arrhythmias, so speak with your vet to ensure this medication is right for them. Giving diltiazem with certain medications can result in health risks to your pet, so discuss your pet’s medications, including vitamins and supplements, and medical conditions with your veterinarian.

Diltiazem Directions for Dogs

Follow the directions on the drug label or as provided by your veterinarian. Your veterinarian will determine the appropriate dosage based on your pet’s weight and their heart condition.

Follow the directions closely. Do not give more or less than as directed by your veterinarian and ensure that this medication is given exactly as scheduled.

Diltiazem can be given with or without food. Giving it with a small meal may help reduce vomiting or other digestive upset.

Missed a Dose?

Speak with your veterinarian about what to do if you forget to give a dose of diltiazem.

Generally, it is critical to give this medication exactly on schedule. If your pet has become off schedule while on this medication, speak with your veterinarian to clarify if any adjustments to their dosing schedule need to be made and for guidance on how to start them back up on a normal dosing schedule.

If you forget to give a dose and then administer it as soon as you remember, your veterinarian may recommend waiting the usual amount of time between the next doses.

Do not give extra or double doses.

Possible Side Effects of Diltiazem in Dogs

Diltiazem is typically well tolerated in most pets. Common symptoms of diltiazem in dogs and cats include:

• Lethargy

• Vomiting

• Diarrhea

• Inappetence (lack of appetite)

• Bradycardia (a heart rate that is too slow)

• Low blood pressure

• Weight loss

• Skin rash

Cats receiving the extended-release version of this medication were more likely to exhibit symptoms of lethargy, vomiting, diarrhea, and weight loss than those not receiving the extended-release version.

Human Side Effects  

Diltiazem is also a prescription medication for humans, frequently with dosages different from those prescribed for your pet by a veterinarian.

Due to possible side effects, humans should never use medicine dispensed for their pets, and pets should not be given any medicine dispensed for a human’s use.

If you accidentally ingest this medication, immediately seek medical attention or call the national Poison Control Center hotline at 1-800-222-1222. 

Monitoring Your Pet

Periodic recheck exams to monitor your pet’s heart health while on diltiazem are necessary. 

Your veterinarian may recommend additional testing depending on your pet's individual needs, other medications they may be on, and/or the issue that initially caused your pet to be placed on this medication.

When To Call Your Vet

Call your veterinarian if any of the following apply:

• You see severe side effects (see above)

• Your pet’s condition worsens or does not improve with treatment

• You see or suspect an overdose

• You have additional questions or concerns about the use of diltiazem

Diltiazem Overdose in Dogs Information

Overdoses of diltiazem are likely to cause exaggerated versions of the side effects noted above, with lethargy, low blood pressure, and arrhythmias that cause slow heart rates being the most common symptoms.

Treatment of overdoses usually involves hospitalization of the pet, so if you suspect an overdose, immediately seek emergency veterinary care or contact an animal poison control center. Consultation fees often apply.

• Pet Poison Helpline® 855-764-7661

• ASPCA® Animal Poison Control 888-426-4435

How To Store Diltiazem for Dogs

Follow these tips when storing your pet’s diltiazem:

• Diltiazem should be stored at controlled room temperatures of 68–77 degrees F (20–25 degrees C). Brief exposure to temperatures 59–86 degrees F (15–30 degrees C) is acceptable.

• Keep the container tightly closed to protect from moisture and light. Always confirm storage requirements by reviewing the label.

• Compounded medications should be stored according to the compounding pharmacy’s label.

• Keep out of reach of children and pets.