Captopril (Capoten®)

Overview

Captopril belongs to a general class of drugs known as angiotensin converting enzyme inhibitors (ACE-inhibitors). Other related drugs in this class include benazepril (Lotensin®), enalapril (Vasotec®), fosinopril (Monopril®), lisinopril (Prinivil, Zestril®), moexipril (Univasc®), quinapril (Accupril®), ramipril (Altace®) and trandolapril (Mavik®).

Captopril decreases the formation of compounds and hormones that constrict blood vessels in animals with heart and vascular disease. Over-production of these compounds can cause narrowing of the blood vessels, high blood pressure and decreased blood flow to organs. 

Therefore, the ACE-inhibitors often are classified as vasodilators because of their relaxing effect on blood vessels. 

These drugs also reduce the concentrations of harmful chemicals and hormones that injure heart muscle in animals with heart failure. 

Captopril is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.

This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names

This drug is registered for use in humans only.

Human formulations: Capoten® (Bristol-Myers Squibb) and various generic preparations

Veterinary formulations: None

Uses of Captopril

The primary use of captopril is for treatment and sometimes prevention of heart failure. Captopril and related drugs are also used to treat high blood pressure. 

Precautions and Side Effects 

While generally safe and effective when prescribed by a veterinarian, captopril can cause side effects in some animals.

Captopril should not be used in animals with known hypersensitivity or allergy to the drug.

Captopril may relax blood vessels to such a degree that some animals become weak due to low blood pressure. 

Less commonly, captopril may affect the blood supply to the kidneys leading to kidney failure. This is most common in dogs and cats treated with higher doses of the drug. It is also more common in animals with kidney disease and when diuretic drugs (such as furosemide) are administered. 

Captopril may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with captopril. Such drugs include furosemide, spironolactone and non-steroidal anti-inflammatories.

Side effects include changes in urination, decreased appetite, vomiting, sudden lethargy or weakness. Side effects are more likely when captopril is given with other potent drugs, such as diuretics or drugs that act to relax blood vessels. 

How Captopril Is Supplied 

Captopril is available in 12.5 mg, 25 mg, 50 mg and 100 mg tablets. 

Dosing Information 

Medication should never be administered without first consulting your veterinarian. 

The typical dose administered to dogs is 0.25 to 1 mg per pound (0.5 to 2 mg/kg) once or two to three times a day orally. 

For cats, the typical dose is 1/4 to 1/2 of a 12.5 mg tablet two to three times a day orally. 

Frequently captopril is given with other drugs, especially in pets undergoing treatment for heart failure or severe high blood pressure. In these situations, a lower initial dose may be prescribed to allow the pet time to get used to the new medication.

The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse.