Attenuation of the pressor response to exogenous angiotensin by angiotensin receptor blockers and benazepril hydrochloride in clinically normal cats

Abstract

OBJECTIVE To compare the attenuation of the angiotensin I-induced blood pressure response by once-daily oral administration of various doses of angiotensin receptor blockers (irbesartan, telmisartan, and losartan), benazepril hydrochloride, or lactose monohydrate (placebo) for 8 days in clinically normal cats. ANIMALS 6 healthy cats (approx 17 months old) with surgically implanted arterial telemetric blood pressure-measuring catheters. PROCEDURES Cats were administered orally the placebo or each of the drug treatments (benazepril [2.5 mg/cat], irbesartan [6 and 10 mg/kg], telmisartan [0.5, 1, and 3 mg/kg], and losartan [2.5 mg/kg]) once daily for 8 days in a crossover study. Approximately 90 minutes after capsule administration on day 8, each cat was anesthetized and arterial blood pressure measurements were recorded before and after IV administration of each of 4 boluses of angiotensin I (20, 100, 500, and 1,000 ng/kg). This protocol was repeated 24 hours after benazepril treatment and telmisartan (3 mg/kg) treatment. Differences in the angiotensin Iinduced change in systolic arterial blood pressure (SBP) among treatments were determined. RESULTS At 90 minutes after capsule administration, only losartan did not significantly reduce ∆SBP in response to the 3 higher angiotensin doses, compared with placebo. Among drug treatments, telmisartan (3 mg/kg dosage) attenuated ∆SBP to a significantly greater degree than benazepril and all other treatments. At 24 hours, telmisartan was more effective than benazepril (mean ± SEM SBP, 15.7 ± 1.9 mm Hg vs 55.9 ± 12.42 mm Hg, respectively). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that telmisartan administration may have advantages over benazepril administration for cats with renal or cardiovascular disease.