Evaluation of oral telmisartan administration as a suppression test for diagnosis of primary hyperaldosteronism in cats

Abstract Background Development of a telmisartan‐based suppression test may facilitate the diagnosis of primary hyperaldosteronism (PHA) in cats, which remains difficult today. Objectives To develop a telmisartan suppression test (TST) that is safe, and able to suppress aldosterone secretion in healthy cats but not in cats with PHA. Animals Ten healthy cats and 6 cats with PHA. Methods Prospective study using a placebo‐controlled crossover design to investigate a TST in healthy cats, and evaluation of TST in cats with PHA. Plasma aldosterone concentration, potassium concentration, and systolic blood pressure (SBP) were measured before (T0), and 1 hour (T1) and 1.5 hours after (T1.5) PO administration of 1 mg/kg of telmisartan, 2 mg/kg of telmisartan or placebo. Results Median age in healthy cats was 3 years old (range, 1‐7). In healthy cats, a telmisartan dose of 2 mg/kg significantly decreased aldosterone concentration at T1 and T1.5 compared with T0. Placebo had no significant effect on aldosterone concentration. In cats diagnosed with PHA, a 2‐mg/kg dose of telmisartan did not induce any significant change in aldosterone concentration at T1 or T1.5 compared with T0. No adverse effects of telmisartan (e.g., hyperkalemia, systemic hypotension) were observed in any cats. Conclusions and Clinical Importance The oral TST shows promise as a diagnostic test for the diagnosis of PHA in cats.