Effect of amlodipine on the circulating renin‐angiotensin‐aldosterone system in healthy cats

Abstract Background Systemic hypertension (SH) is a common cardiovascular disease in older cats that is treated primarily with the calcium channel blocker amlodipine besylate (AML). The systemic effect of AML on the classical and alterative arms of the renin‐angiotensin‐aldosterone system (RAAS) in cats is incompletely characterized. Hypothesis/Objectives To determine the effect of AML compared to placebo on circulating RAAS biomarkers in healthy cats using RAAS fingerprinting. Animals Twenty healthy client‐owned cats. Methods Cats were administered amlodipine besylate (0.625 mg in toto) or placebo by mouth once daily for 14 days in a crossover design with a 4‐week washout period. Plasma AML concentrations and RAAS biomarker concentrations were measured at multiple timepoints after the final dose in each treatment period. Time‐weighted averages for RAAS biomarkers over 24 hours after dosing were compared between treatment groups using Wilcoxon rank‐sum testing. Results Compared to placebo, AML treatment was associated with increases in markers of plasma renin concentration (median 44% increase; interquartile range [IQR] 19%‐86%; P = .009), angiotensin I (59% increase; IQR 27‐101%; P = .006), angiotensin II (56% increase; IQR 5‐70%; P = .023), angiotensin IV (42% increase; −19% to 89%; P = .013); and angiotensin 1‐7 (38% increase; IQR 9‐118%; P = .015). Conclusions and Clinical Importance In healthy cats, administration of AML resulted in nonspecific activation of both classical and alternative RAAS pathways.