Amlodipine for feline systemic hypertension — LIKELY

In hypertensive cats, does amlodipine vs placebo lower systolic blood pressure — and does dose titration matter?

Shelf #249 · gate-verified and displayed under the developer's blinded-trial rule

LIKELY: Amlodipine lowers systolic blood pressure in hypertensive cats, on the strength of one randomised, double-blind, placebo-controlled trial, supported by a dose analysis of treated cats — the single placebo-controlled trial is stated on the face of this shelf. In Huhtinen 2015 (77 client-owned hypertensive cats), 63% of amlodipine cats were responders (systolic pressure < 150 mmHg at day 28, or a fall from baseline of ≥ 15%) vs 18% on placebo; amlodipine cats were 7.9 times more likely to respond (95% CI 2.6–24.1, P < .001), and systolic pressure fell from a mean baseline of 181 (± 12) mmHg to 154 (± 17) mmHg on amlodipine vs 170 (± 21) mmHg on placebo. Bijsmans 2016 (100 treated hypertensive cats, no control group) found most cats reach a systolic pressure < 160 mmHg on 0.625 or 1.25 mg once daily, and that cats starting with higher pressure need the higher dose: median pressure at diagnosis was 207 [194, 217] mmHg in the 1.25 mg group vs 182 [175, 192] mmHg in the 0.625 mg group (P < .001). Drafted Nov 10, 2026 (VetMed build, topic #249); all figures from abstracts fetched and verified at drafting.

Huhtinen 2015: chewable amlodipine — 63% responders vs 18% on placebo in 77 hypertensive cats

Randomised, double-blind, placebo-controlled trial (28-day blinded phase, then open-label amlodipine)

Who: Cats: 77 client-owned cats with systemic arterial hypertension (median age 14 years), in a randomized, double-blinded, placebo-controlled study — 42 cats received 0.125–0.50 mg/kg amlodipine (chewable tablets) once daily for 28 days and 35 received placebo; after 28 days all cats continued on amlodipine for 2–3 months in an open-label phase. Blood pressure was measured by high-definition oscillometry. Sixty-one cats completed the study.

Result: The responder rate (systolic blood pressure < 150 mmHg at 28 days, or a decrease from baseline ≥ 15%) was 63% in the amlodipine group and 18% in the placebo group; cats receiving amlodipine were 7.9 (95% CI 2.6–24.1) times more likely to be classified as responders (P < .001). From a mean (± SD) baseline of 181 (± 12) mmHg, systolic pressure decreased to 154 (± 17) mmHg with amlodipine and to 170 (± 21) mmHg with placebo (P < .001). Voluntary acceptance of the chewable formulation was 73%, the tablets were well tolerated, and the record states the drug can be used concomitantly with angiotensin-converting enzyme inhibitors and in cats with chronic kidney disease.

Watch out: The blinded comparison lasts only 28 days; everything after that is open-label. The endpoint is blood pressure itself — a process measure — not target-organ outcomes such as retinal or renal events, which this trial does not report. Sixteen of 77 enrolled cats did not complete the study, per the record's completion count.

Huhtinen M, Derré G, Renoldi HJ, Rinkinen M, Adler K, Aspegrén J, Zemirline C, Elliott J. Randomized placebo-controlled clinical trial of a chewable formulation of amlodipine for the treatment of hypertension in client-owned cats. J Vet Intern Med. 2015;29(3):786-93. PMID: 25857394. Registry ID: none in the record. MeSH: Administration, Oral · Amlodipine · Animals · Antihypertensive Agents · Cat Diseases · Cats · Double-Blind Method · Female · Hypertension · Male · Tablets

Bijsmans 2016: cats starting with higher pressure needed 1.25 mg rather than 0.625 mg amlodipine to reach target

Cross-sectional dose-response analysis of amlodipine-treated hypertensive cats (no untreated control group)

Who: Cats: 100 hypertensive cats that had reached a target systolic blood pressure of < 160 mmHg on amlodipine besylate — 59 cats requiring 0.625 mg (group A) and 41 requiring 1.25 mg (group B) once daily; plasma amlodipine concentrations were measured. Indexed in the record as a cross-sectional study; there is no placebo or untreated group.

Result: Cats requiring the greater dose had significantly higher systolic pressure at diagnosis (group A: median [25th, 75th percentile] 182 [175, 192] mmHg; group B: 207 [194, 217] mmHg, P < .001), but comparable blood pressure was achieved after treatment. Plasma amlodipine concentrations were directly related to the dose administered, and the decrease in systolic pressure was directly and independently associated with the pressure at diagnosis and the plasma amlodipine concentration. At diagnosis, group B cats had lower plasma potassium (A: 4.1 [3.8, 4.5]; B: 3.8 [3.6, 4.2] mEq/L, P < .01); weight did not differ between groups.

Watch out: This is a dose-requirement analysis of cats already controlled on amlodipine, not a trial of whether amlodipine works — it cannot add efficacy evidence, only dosing evidence. Differences in amlodipine pharmacokinetics between cats did not seem to explain the response, per the record.

Bijsmans ES, Doig M, Jepson RE, Syme HM, Elliott J, Pelligand L. Factors Influencing the Relationship Between the Dose of Amlodipine Required for Blood Pressure Control and Change in Blood Pressure in Hypertensive Cats. J Vet Intern Med. 2016;30(5):1630-1636. PMID: 27717190. Registry ID: none in the record. MeSH: Amlodipine · Animals · Antihypertensive Agents · Blood Pressure · Cat Diseases · Cats · Cross-Sectional Studies · Dose-Response Relationship, Drug · Female · Hypertension · Male

Synthesis: one decisive placebo-controlled trial for efficacy, one treated-cat analysis for dose

Synthesis

Who: Synthesis of the cards above: Huhtinen 2015 (randomised double-blind placebo-controlled trial, 77 cats) and Bijsmans 2016 (cross-sectional analysis, 100 amlodipine-treated cats).

Result: The efficacy claim rests on a single placebo-controlled trial, and it is a clear one: a 63% vs 18% responder split and a mean systolic fall to 154 mmHg on amlodipine against 170 mmHg on placebo over 28 days. The dosing claim rests on treated-cat data: 0.625 mg once daily controls most cats, and a starting systolic pressure around or above 200 mmHg predicts needing 1.25 mg. Blood pressure is the treatment target in feline hypertension, but neither card measures whether treatment prevents blindness, kidney progression or death.

Watch out: A single placebo-controlled trial, however clear, is why this shelf is LIKELY rather than PROBABLE; the second card is uncontrolled by design and is carded for dose only. Only the trial report describes its measurement method and cohort: Huhtinen measured blood pressure by high-definition oscillometry in cats of median age 14 years; the Bijsmans record states neither a measurement method nor the ages of its cats.

Synthesis of Huhtinen M et al. PMID: 25857394; Bijsmans ES et al. PMID: 27717190. Registry IDs as on the individual cards.

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