Coleman AE, Brown SA, Traas AM, Bryson L, Zimmering T, et al. Safety and efficacy of orally administered telmisartan for the treatment of systemic hypertension in cats: Results of a double-blind, placebo-controlled, randomized clinical trial. J Vet Intern Med. 2019 Mar 9
Hypertension, or high blood pressure, is a common issue in domestic cats. This may occur as a result of chronic kidney disease, hyperthyroidism, or potentially spontaneously. Regardless of the cause, hypertension leads to significant end organ damage including blindness, neurologic deficits, and progression of kidney disease. Management of hypertension is essential and is usually accomplished by use of the drug amlodipine. However, some cats do not tolerate amlodipine or do not achieve sufficient control. While effective at controlling blood pressure, amlodipine does not treat the underlying activation of the renin-angiotensin-aldosterone system (RAAS), and may in fact lead to increased RAAS activation.
Telmisartan is an angiotensin receptor blocker that has been labelled in several countries
for the management of proteinuria. Several studies have determined its efficacy in decreasing blood pressure in cats. This study was designed as a prospective, double blinded, randomized, placebo controlled multicenter clinical trial. An initial 28 day parallel group phase was followed by a 154 day open label extended use phase.
Client owned cats with indirect systolic blood pressures between 160-200mmHg by doppler were recruited from participating clinics. Cats were stratified by underlying disease (CKD, hyperthyroidism, both, or neither), and all concurrent disease was required to be stable. Cats were excluded for the use of blood pressure modifying drugs or a range of conditions known to effect blood pressure.
Telmisartan was administered to cats at 1.5mg/kg PO q12h for 14 days, then 2mg/kg q24h. Placebo cats were administered an equal volume of visually identical inactive solution. Blood pressure was rechecked at 14 and 28 days, and then cats in the treatment group with a blood pressure <180 were given the option to extent to a 154 day extended use phase, in which blood pressure was rechecked at 56, 98, 140, and 182 days. If blood pressures reached <120mmHg drug dose was reduced, and cats were dropped from the trial and transitioned to an alternative drug if pressures >180 were measured.
221 cats from 20 trial sites were enrolled (from an initial screened population of 7605 cats from 33 sites) of which 121 received telmisartan, and 107 entered the extended use phase.
On day 14, the drop in BP in telmisartan treated cats was 23.3mmHg, compared to 7.5mmHg for placebo cats, a significant difference. This significance was maintained through day 28. A “response” to therapy was defined as a reduction of SBP to <150mmHg f 15% of baseline. With these criteria, 52% of cats were responders on day 14, 52.9% on day 28, and 57.8%, 71.7%, 64.2%, and 63% on days 56, 98, 40, and 182 respectively. The study was not powered to detect differences in response to telmisartan based on disease type.
The incidence of adverse events in the blinded phase were similar in placebo and treatment group and usually attributable to advanced age and concurrent disease. Most adverse effects were gastrointestinal, with multiple day vomiting being more common in the treatment group. Hypotension was reported in 4 cats in the initial phase and 3 cats in the extension phase.
The authors of this study conclude that telmisartan was safe and effective in reducing blood pressure in this population of hypertensive geriatric cats. The drug experienced no reduction in efficacy with time, and adverse effects were minimal and generally not directly related to the drug use.
Some drawbacks exist to the widespread use of telmisartan for hypertension at this point. These include the significant volume needed with current formulations, increase cost compared to amlodipine, and an unclear long term survival benefit. However, this data suggests that telmisartan may be a safe and effective option for the management of hypertension in cats.
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