Captopril for Dogs

Updated Nov. 21, 2023
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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 Captopril?

Captopril is the first available ACE (angiotensin-converting enzyme) inhibitor used in dogs to treat congestive heart failure (CHF) and high blood pressure (hypertension).

However, captopril has fallen out of favor when compared to newer ACE inhibitor medications such as enalapril and benazepril. Captopril is less effective, has more adverse effects, and does not last as long, which requires more doses per day. Due to these considerations, captopril is not commonly prescribed, and when it is, it is typically used in combination with other cardiac medications to manage hypertension and heart failure.

Captopril is FDA-approved for human use as generic captopril. The brand name Capoten® has been discontinued. Captopril is currently not FDA-approved as a veterinary medication. However, it is readily utilized in the veterinary field, and veterinarians can legally prescribe certain human drugs in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label.

Captopril Considerations

Captopril should not be used in pets who are hypersensitive to ACE inhibitors. Captopril should be used with caution in pets with certain medical conditions, including kidney disease, low sodium level (hyponatremia), diseases that affect blood flow to the brain (cerebrovascular insufficiency), preexisting blood cell abnormalities, skin conditions of collagen and blood vessels such as systemic lupus erythematosus (SLE), and pregnancy.

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

Treatment with captopril requires intensive monitoring and close supervision by your veterinarian, particularly if your pet has severe congestive heart failure (CHF). Before and during your pet’s treatment, your vet may perform blood and urine tests to evaluate the effects of captopril on the kidneys, monitor blood pressure measurement, and order periodic chest X-rays, and/or an ECG (electrocardiogram).

How Captopril Works

Captopril is classified as an ACE (angiotensin-converting enzyme) inhibitor. ACE inhibitors help pets with heart disease by lowering blood pressure and widening blood vessels. They block angiotensin-converting enzymes that are responsible for constricting blood vessels in the body.

Once that enzyme has been blocked, the blood vessels relax and stay open. This decreases blood pressure and allows blood to circulate smoothly throughout the body, thereby increasing blood supply and oxygen to the heart.

Captopril Directions

Follow the directions on the drug label or as provided by your veterinarian.

Captopril is best absorbed if given on an empty stomach. If your pet vomits, has diarrhea, or acts sick after receiving the drug on an empty stomach, contact your veterinarian.

Your pet should have access to water at all times while on this medication.

Do not stop or reduce your pet’s dose unless instructed by your veterinarian. If your veterinarian recommends that you discontinue captopril for any reason, they will typically recommend that you wean your pet off the medication slowly, and under their supervision.

It is important to note that safe use has not been established in breeding, pregnant, or lactating dogs.

Your vet may reduce your pet’s dosage of captopril if they have kidney disease.

Missed a Dose?

Speak with your veterinarian about what to do if you forget to give a dose of captopril. Generally, they may instruct you to give it when you remember, or if it is almost time for your pet’s next dose, to skip the missed dose and resume your normal dosing schedule. Do not give extra or double doses.

Captopril Possible Side Effects

Side effects of captopril may include:

  • Gastrointestinal upset (vomiting and diarrhea)

  • Weakness, low energy, and fainting due to low blood pressure (hypotension)

  • Kidney injury

  • High potassium level (hyperkalemia)

Human Side Effects

Captopril 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.

In people, captopril can cause injury and death to a developing fetus. If you are pregnant, trying to become pregnant, or breast-feeding, ensure that you do not ingest this medication or talk to your veterinarian about the possibility of administering an alternative medication to your pet.

If you accidentally ingest this medication, immediately call your physician or the national Poison Control Center hotline at 800-222-1222.

Call Your Vet If:

  • Severe side effects are seen (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 captopril

Captopril Overdose Information

Signs of a captopril overdose may include abnormally low blood pressure (hypotension), low energy (lethargy), weakness, fainting (syncope), or collapse.

If you suspect an overdose, immediately contact your veterinarian, seek emergency veterinary care, or call an animal poison control center. Consultation fees often apply.

Pet Poison Helpline (855) 764-7661

ASPCA Animal Poison Control (888) 426-4435

Captopril Storage

Always confirm storage requirements by reading the prescription label.

Captopril should be stored at controlled temperatures from 68 to 77 F.

Keep the container tightly closed in order to protect its contents from moisture and light.

Keep out of reach of children and pets.

Captopril for Dogs FAQs

What is the difference between captopril and lisinopril?

Captopril and lisinopril are both classified as ACE inhibitors. Compared to captopril, lisinopril is a newer medication, lasts longer, and is considered more effective. Like captopril, there is limited clinical information available for the use of lisinopril in animals.

What are the most common side effects of captopril in dogs?

Captopril may cause side effects including gastrointestinal upset (vomiting, diarrhea) and fainting due to low blood pressure (hypotension).

No vet writer or qualified reviewer has received any compensation from the manufacturer of the medication as part of creating this article. All content contained in this article is sourced from public sources or the manufacturer.

Featured Image: Liudmila Chernetska/iStock via Getty Images Plus


Morisse B, Kersten U. Treatment of heart failure in dogs with ACE inhibitors: comparison of quinapril and captopril. Tierarztliche Praxis. 1995 Oct;23(5):489-96.



Molly Price, DVM


Molly Price, DVM


Dr. Molly Price has practiced small animal medicine for over 20 years and is a graduate of Texas A&M College of Veterinary Medicine. She...

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