Benazepril use in cats

Fortekor 5mg packages have the active ingredient benazepril, indicated for the treatment of heart failure, chronic renal insufficiency and hypertrophic cardiomyopathy (HCM) in cats. Benazepril reduces protein loss in urine and lowers systemic and intraglomerular blood pressure, thus increasing quality of life.

Benazepril has been shown to increase the survival times in cats with a urinary protein/creatinine ratio (UPC) equal to or exceeding 0.8 before treatment ( moderate proteinuria), and to improve the appetite in cats with a UPC ratio exceeding 1.0. Benazepril has some beneficial effects on clinical signs and cardiac remodelling in cats with feline hypertrophic cardiomyopathy and is well tolerated. Most cases of HCM in cats will require other medications in addition to benazepril, such as a calcium channel blocker, e.g. diltiazem.

Pharmacological properties

Benazepril is a prodrug hydrolyses in vivo to benazeprilat, which inhibits the angiotensin converting enzyme (ACE), thus preventing the conversion of inactive angiotensin I into active angiotensin II. Benazepril reduces all effects mediated by angiotensin II, including vasoconstriction of both arteries and veins and retention of sodium and water by the kidney, Benazepril causes long-lasting inhibition of plasma ACE in cats, with significant inhibition persisting for 24 hrs after a single dose.

Benazepril is rapidly but incompletely absorbed from the gastrointestinal tract following oral administration. Absorbed benazepril is partially hydrolysed by hepatic enzymes to the active substance, benazeprilat; unchanged benazepril and hydrophilic metabolites account for the remainder. Peak plasma benazeprilat concentrations are attained within about 2 hrs both in fasting and fed situations. Benazepril and benazeprilat are bound to plasma proteins, and in tissues are found mainly in liver and kidney. The major part of benazeprilat is rapidly eliminated, although there is  in addition a slow terminal elimination phase. Benazeprilat is excreted primarily via the biliary route in cats. Repeated administration of benazepril daily, leads to slight accumulation of benazeprilat in plasma; steady state is attained within four days. Because of its biliary excretion route, there is little risk of bioaccumulation of benazeprilat  in cats with impaired renal function. For this reason no dose adjustment of benazepril is necessary in cases of renal insufficiency.

Precautions

Benazepril may increase plasma creatinine concentrations at the start of therapy. This effect is related to the therapeutic effect of the product in reducing glomerular capillary blood pressure and therefore it is not necessarily a reason to stop therapy in the absence of other signs. Benazepril reduces erythrocyte counts in normal cats at high doses, but this effect was not observed at the recommended dose during clinical trials in cats with chronic renal insufficiency. Therefore, as is routine in cases of chronic renal insufficiency, it is recommended to monitor plasma creatinine and erythrocyte counts during therapy.

Benazepril has not been tested in cats under 2.5 kg body weight or in pregnant or lactating queens. It should therefore be used with precaution in these animals and only used if justified clinically, considering the risk/benefit ratio. Benazepril reduced ovary/oviduct weights when administered daily at 10 mg/kg for 25 weeks. ACE inhibitors have been found to be teratogenic in the second and third trimesters in other species.

There are no known reactions between benazepril and other medications in cats. The combination of ACE inhibitors and other antihypertensive agents (e.g. calcium channel blockers, beta-blockers or diuretics) may lead to additive hypotensive effects.