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Pharmacological particulars
Pharmacotherapeutic group: ACE Inhibitors, plain.
ATCvet code: QC09AA07
Pharmacodynamic properties
Benazepril hydrochloride is a prodrug hydrolysed in vivo to its active metabolite, benazeprilat. Benazeprilat is a highly potent and selective inhibitor of ACE, thus preventing the conversion of inactive angiotensin I to active angiotensin II and thereby also reducing synthesis of aldosterone. Therefore, it blocks effects mediated by angiotensin II and aldosterone, including vasoconstriction of both arteries and veins, retention of sodium and water by the kidney and remodelling effects (including pathological cardiac hypertrophy and degenerative renal changes).
FORTEKOR Flavour causes long-lasting inhibition of plasma ACE activity, with more than 95% inhibition at peak effect and significant activity (>80% in dogs) persisting 24 hours after dosing.
FORTEKOR Flavour reduces the blood pressure and volume load on the heart in dogs with congestive heart failure.
Pharmacokinetic particulars
After oral administration of benazepril hydrochloride, peak levels of benazepril are attained rapidly (Tmax 0.5 hour in dogs) and decline quickly as the active substance is partially metabolised by liver enzymes to benazeprilat. The systemic bioavailability is incomplete (~13% in dogs) due to incomplete absorption (38% in dogs) and first pass metabolism.
In dogs, peak benazeprilat concentrations (Cmax of 37.6 ng/ml after a dose of 0.5 mg/kg benazepril hydrochloride) are achieved with a Tmax of 1.25 hours.
Benazeprilat concentrations decline biphasically: the initial fast phase (t1/2=1.7 hours in dogs) represents elimination of free drug, while the terminal phase (t1/2=19 hours in dogs) reflects the release of benazeprilat that was bound to ACE, mainly in the tissues. Benazepril and benazeprilat are extensively bound to plasma proteins (85-90%), and in tissues are found mainly in the liver and kidney.
There is no significant difference in the pharmacokinetics of benazeprilat when benazepril hydrochloride is administered to fed or fasted dogs. Repeated administration of FORTEKOR Flavour leads to slight bioaccumulation of benazeprilat (R=1.47 in dogs with 0.5 mg/kg), steady state being achieved within a few days (4 days in dogs).
Benazeprilat is excreted 54% via the biliary and 46% via the urinary route in dogs. The clearance of benazeprilat is not affected in dogs with impaired renal function and therefore no adjustment of FORTEKOR Flavour dose is required in cases of renal insufficiency.