Randomized Placebo-Controlled Clinical Trial of a Chewable Formulation of Amlodipine for the Treatment of Hypertension in Client-Owned Cats

Abstract

Background: There is an unmet clinical need for a cat-specific formulation of amlodipine to treat hypertensive cats. Objectives: To assess the efficacy of chewable amlodipine tablets in reducing systolic blood pressure (SBP) in cats diagnosed with systemic arterial hypertension. Animals: Seventy-seven client-owned cats with systemic hypertension were included (median age 14 years). Methods: The study was randomized, double-blinded, and placebo-controlled. Forty-two cats received 0.125-0.50 mg/kg amlodipine once daily for 28 days; 35 cats received placebo. After 28 days all cats continued with amlodipine for 2-3 months in an open-label phase. Blood pressure was measured using high definition oscillometry. A responder was defined as a cat showing a decrease of SBP to <150 mmHg at 28 days or a decrease from baseline ≥15%. Results: Sixty-one cats completed the study. The responder rate was 63% in amlodipine group and 18% in placebo group. Cats receiving amlodipine were 7.9 (95% CI 2.6-24.1) times more likely to be classified as responders when compared to those receiving placebo (P < .001). From a mean (±SD) baseline value of 181 (±12) mmHg, SBP decreased to 154 (±17) mmHg with amlodipine and to 170 (±21) mmHg with placebo (P < .001). The voluntary acceptance rate of amlodipine formulation was 73%. Conclusions and Clinical Importance: The chewable amlodipine tablet effectively reduced SBP compared with placebo in hypertensive cats, and was well-tolerated. It can be used concomitantly with angiotensin-converting enzyme inhibitors and in cats with chronic kidney disease.