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Benazepril for veterinary use
by Barbara Forney, VMD
Benazepril is an angiotensin converting enzyme (ACE) inhibitor. It is used as a vasodilator in the treatment of congestive heart failure (CHF), systemic hypertension, chronic renal failure and protein losing nephropathies. Studies in human medicine indicate that ACE inhibitor drugs improve exercise tolerance, improve quality of life and prolong life in heart failure patients.
Benazepril is a pro-drug which is metabolized by the liver into its active form, benazeprilat. In the active form, this drug blocks the conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor. When its concentrations are decreased, peripheral vascular resistance, blood pressure, and aldosterone levels decrease, and plasma renin activity increases. Benazepril is rapidly absorbed after oral administration and is primarily eliminated by the kidneys. Although the liver metabolizes benazapril to the active form, liver dysfunction does not appear to significantly decrease the levels of benazeprilat.
Dogs and cats
ACE inhibitor drugs, such as benazepril and enalapril are considered mainstays for the treatment of CHF in dogs and cats. Benazepril is a particularly useful drug for the treatment of hypertension in dogs. While benazepril alone may be used to treat mild hypertension in cats, amlodipine or a combination of benazepril and amlodipine may be more effective in treating cats with severe hypertension. Benazepril may be combined with amlodipine, or beta-blockers in refractory cases of hypertension.
Benazepril is used to treat chronic renal failure and proteinuria in both dogs and cats. 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. Benazepril has been shown to increase renal plasma flow and glomerular filtration rates in cats. It has also been shown to improve appetite in cats with chronic kidney disease. Although the studies on chronic kidney disease in dogs and cats show positive trends, there have not been studies that indicate a significant increase in survival time.
- Adverse effects due to ACE inhibitors are rare.
- Hypotension, weakness, lethargy, GI upset (anorexia, vomiting, diarrhea), hyperkalemia, and renal dysfunction.
- Although benazepril 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.
- Patients receiving benazepril should be monitored regularly for arterial blood pressure, renal function, and serum electrolytes.
- ACE inhibitors should not be used in animals that have pre existing hypotension, hypovolemia, hyponatremia, or are in acute renal failure.
- Hydration status should be checked and corrected before starting an animal on benazapril.
- Benazepril should be avoided in pregnant or lactating animals.
- Diuretics and other vasodilators may increase the incidence of hypotension or hyperkalemia. ACE inhibitors may increase the effect of diuretic drugs. Careful monitoring and adjustment of drug therapies may be necessary to reach the optimal therapeutic balance.
- Potassium sparing diuretics or potassium supplements may increase the risk of hyperkalemia.
- NSAIDs including aspirin should be avoided in animals on benazapril due to an increased risk of acute renal failure.
- Concurrent use of benazepril and insulin may increase the risk of hypoglycemia. Animals may require additional monitoring.
- Concurrent use of benazepril and lithium may increase lithium levels. Animals may require additional monitoring.
- If an overdose is recognized promptly, gut emptying protocols should be attempted. Hypotension is the most clinically significant problem when managing an overdose of benazepril. Hospitalization with volume expansion, blood pressure monitoring, and supportive care may be necessary.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
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