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 25-28 September, 2018 | Singapore
absence of TOD if SBB is persistently ≥ 180 mmHg (as measured on > 1 occasion on separate visits measured over one to two weeks).Amlodipine besylate a second-generation dihydropyridine that blocks L-type calcium channels in vascular smooth muscle is the first-choice antihypertensive agent in cats. It is. Due to its long plasma half-life and slow receptor binding and dissociation that results in a relatively slow onset and waning of effect, the drug can be administered once daily orally. To manage SH it is recommended to aim for a target SBP of < 160 mmHg and to recheck SBP one to two weeks after commencing treatment.
The recommended dose rate for cats is 0.125 –
0.5 mg/kg once daily orally, and most cats are administered 0.625 mg to 1.25 mg/cat at diagnosis. A recent study investigating factors influencing the dose of amlodipine required to change SBP in cats with SH identified that cats with a higher SBP at presentation needed a higher dose of amlodipine to decrease SBP to target levels4. Plasma amlodipine concentrations were directly related to the dose of amlodipine administered. The decrease in SBP was directly and independently associated with the SBP at diagnosis and the plasma amlodipine concentration. Based on these results the authors proposed a starting dose for cats with SBP of ≥200 mmHg of 1.25 mg per cat once a day4.
For cats with SH that have SBP ≥ 160 mmHg after
> 1 week of amlodipine therapy, treatment options include doubling the dose of amlodipine (from 0.25 – 0.5 mg/kg once daily) or combining amlodipine with a RAAS inhibitor, either an angiotensin- converting enzyme inhibitor (ACEi), e.g. benazepril, or an angiotensin II receptor blocker (ARBs),
e.g. telmisartan. The antihypertensive effect of benazepril in cats is relatively mild, thus benazepril is not recommended for first-line therapy of SH in cats.
Telmisartan selectively antagonizes the angiotensin II, subtype 1 (AT1) receptor, the latter which mediates the adverse effects of angiotensin II on the cardiovascular system and kidneys. A field trial evaluating the effect of telmisartan on SB in healthy conscious cats found that doses of telmisartan of 1 – 3 mg/kg/day administered orally as a single dose or split into two equal doses resulted in a significant reduction of SBP and was well tolerated 5. In cats administered placebo Mean ± SBP was 131 ± 15 mmHg at baseline and 124 ± 14 mmHg after 14d. For
cats administered 1 mg/kg telmisartan once daily mean baseline SBP was 130 ± 15 mmHg and after 14 d was 105 ± 10 mmHg, while for cats administered
1 mg/kg telmisartan twice daily baseline SBP was 131 ± 19 mmHg and after 14 d was 91 ± 18 mmHg. Further studies are required to determine dose and efficacy of telmisartan for treatment of feline SH.
Gingival hyperplasia is a dose-dependent adverse event associated with amlodipine administration in humans. Recently, it was described in a cat administered 2.5 mg of amlodipine daily, and resolved after the drug was withdrawn6.
Cats with SH should be monitored after stabilisation at least every three months. Drug dosages should be decreased in cats showing clinical signs of hypotension (e.g weakness) or if SBP < 120 mmHg.
1. Taylor SS, Sparkes AH, Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS, Scansen BA. ISFM Consensus Guidelines on the Diagnosis and Management of Hypertension in Cats. Journal of Feline Medicine and Surgery 2017; 19: 288-303
2. Jepson RE, Syme HM, Elliott J. Plasma renin activity and aldosterone concentrations in hypertensive cats with and without azotaemia and in response to treatment with amlodipine besylate. Journal of Veterinary Internal Medicine 2014; 28: 144 -153.
3. Payne JR, Brodbelt DC, Luis Fuentes V. Blood Pressure Measurements in 780 Apparently Healthy Cats. Journal of Veterinary Internal Medicine 2017; 31: 15 - 21
4. Bijsmans ES, Doig M, Jepson RE, Syme HM, Elliott J, Pellingand L. Factors influencing the Relationship Between the Dose of Amlodipine Required for Blood Pressure Control and Change in Blood Pressure in Hypertensive Cats. Journal of Veterinary Internal Medicine 2016; 30: 1630-1636
5. Coleman AE, Brown SA, Sartk M. Evaluation of orally administered telmisartan for the reduction of indirect systolic arterial blood pressure in awae, clinically normal cats. Journal of Feline Medicine and Surgery 2018; doi: 10.1177/1098612X18761439
6. Desmet L, van der Meer J. Antihypertensive treatment with telmisartan in a cat with amlodipine-induced gingival hyperplasia. Journal of Feline Medicine and Surgery Open Reports 2017; doi: 10.1177/2055116917745236.

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