Enalapril For Veterinary Use

Overview

Therapeutic Class
Angiotensin-converting enzyme (ACE) inhibitor
Species
Dogs and Cats
Commonly prescribed by vets for:
Congestive heart failure (CHF), hypertension, chronic renal-failure, protein-losing nephropathies.
Vet drug status Status
Approved for use in the dog; however, no veterinary products are commercially available.

Basic Information

Enalapril is an ACE inhibitor that blocks the formation of angiotensin II. It is used as a vasodilator in the treatment of CHF and systemic hypertension. It is also used in animals with chronic renal failure and protein-losing nephropathies.

Enalapril acts as a competitive inhibitor of the ACE responsible for converting angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and when its concentrations are decreased, peripheral vascular resistance decreases, blood pressure decreases, aldosterone levels are reduced and plasma-renin activity is increased.

Dogs and cats

Enalapril is used in dogs and cats for the treatment of CHF, occult-dilated cardiomyopathy and systemic hypertension. In large studies of dogs with moderate to severe heart disease due to mitral regurgitation or dilated cardiomyopathy, enalapril improved survival by greater than 100 percent, improved quality of life, improved exercise tolerance and decreased pulmonary edema. When treating CHF in dogs, enalapril is frequently combined with other drugs, such as furosemide, spironolactone or a positive-inotropic drug. Enalapril may be combined with beta-blockers in the treatment of occult-dilated cardiomyopathy or systemic hypertension. The value of enalapril in the treatment of degenerative-mitral valve disease of small breed dogs is still being investigated. While enalapril may be used to treat mild hypertension in cats, alodipine may be more effective for cats with severe hypertension.

Enalapril is used to treat chronic renal failure and proteinuria. By blocking the production of angiotensin II, enalapril causes vasodilation of the glomerular-efferent arterioles, decreases intraglomerular pressure and reduces the glomerular filtration rate (GFR). The improvement in renal function is postulated to be due to the anti-hypertensive effect, the reduction in mesangial-cell proliferation and renal vasodilation, which causes a decrease in renal-filtration pressure and decreased proteinuria.

Side Effects

The most common side effects are hypotension, weakness, lethargy, GI upset (anorexia, vomiting or diarrhea), hyperkalemia and renal dysfunction. Although enalapril is used to treat chronic renal failure, there are instances of mild to moderate reversible renal failure, which may be precipitated by volume depletion superimposed on dilatation of the efferent arterioles.

Precautions

• Patients receiving enalapril should be monitored regularly for arterial blood pressure, renal function and serum electrolytes.

• If an animal shows adverse effects due to enalapril, withdrawal followed by a lower dose or a longer dosing-interval may be helpful. Severely azotemic animals should start with once-a-day dosing while being closely monitored for renal function.

• Some dogs appear to be dependant on the effects of angiotensin II for maintaining GFR. While this is unusual, this subpopulation will not tolerate ACE-inhibitor drugs.

• Enalapril should be avoided in pregnant or lactating animals.

Drug Interactions

• Diuretics and other vasodilators may increase the incidence of hypotension or hyperkalemia. Careful monitoring and adjustment of drug therapies may be necessary to reach the optimal therapeutic balance.


• NSAIDs, including aspirin, should be avoided in animals on enalapril.

Overdose

• If an overdose is recognized promptly, gut-emptying protocols should be attempted. Hypotension is the most clinically significant problem when managing an overdose of enalapril. Hospitalization with volume expansion, blood-pressure monitoring and supportive care may be necessary.