VetMedLatanoprost in cats with glaucoma: does it lower intraocular pressure vs no prostaglandin? — POSSIBLE
In cats with glaucoma, does latanoprost vs no prostaglandin lower intraocular pressure?
Shelf #730 · gate-verified and displayed under the developer's blinded-trial rule
POSSIBLE: In cats with congenital glaucoma — the only feline glaucoma population with controlled latanoprost records — latanoprost lowers intraocular pressure (IOP) acutely for a few hours after a dose, but a sustained lowering of mean IOP has not been shown. In McDonald 2016 (PMID: 26183373; 6 cats with inherited primary congenital glaucoma, latanoprost 0.005% twice daily to one eye and vehicle to the other for 3 weeks), mean IOP was significantly lower in treated than control eyes for up to 8 hours after a single treatment, with a maximal reduction of 63% (relative, as the record states it) at 3 hours and a mean reduction of 16 mmHg (about 33% relative) against pre-treatment values at 3–4 hours on day 1 (PMC full text) — yet there were no statistically significant changes in weekly mean peak IOP between treated and control eyes during any week, and no tendency for IOP to be reduced over time. In Yang 2026 (PMID: 39609901; masked controlled crossover, 5 cats with feline congenital glaucoma), latanoprost reduced mean IOP relative to saline-treated control eyes by 5.5 mmHg (95% CI −8.4 to −2.5, p < .001) at 4 hours, a 28.4% relative reduction, and the authors state these reductions were not considered clinically significant. In normal (non-glaucomatous) cats neither study found a significant IOP reduction, and the healthy-cat record (Studer 2000, PMID: 11039551) agrees — but healthy cats are not this shelf's population and are not carded. Design class (a): randomisation and masking are established by Yang 2026, a masked crossover in which latanoprost was given in a randomized eye with saline-treated contralateral controls, answering this shelf's own comparison in glaucomatous cats — flagged below for its eye-level randomisation and five-cat sample, and for its partial masking (the full text states observers were masked to the test drug administered but could not be masked to the treated eye, because of the miotic effect of prostaglandin analogs); McDonald 2016 on its own would be class (c), because its full text states no effort was made to mask the observer or randomize the eye treated. The stamp is POSSIBLE, not LIKELY, because the glaucomatous evidence totals 11 cats, both studies are in congenital glaucoma only, and the demonstrated effect is transient (hours after a dose) rather than a sustained mean-IOP reduction. Tier C is not engaged: no mortality or survival claim is made. Drafted Nov 10, 2026 (VetMed build, topic #730); figures from the abstracts and, for McDonald 2016, the PMC full text, fetched and verified at drafting.
McDonald 2016: latanoprost acutely lowered IOP in congenital-glaucoma cats (maximal 63% relative reduction at 3 hours; 16 mmHg mean reduction vs pre-treatment), but weekly mean peak IOP did not differ between treated and control eyes over 3 weeks
Controlled contralateral-eye study, NOT randomised and NOT masked (full text's own wording, quoted on the card; publication types: Clinical Trial, Journal Article)
Who: Cats: 12 adult cats — 6 normal and 6 with inherited primary congenital glaucoma (PCG) — in a controlled contralateral-eye study. Intraocular pressure (IOP) and pupil diameter were measured in both eyes three times per week for 3 weeks before, 3 weeks during and 2 weeks after twice-daily treatment with latanoprost 0.005% to the right eye and vehicle to the left (control) eye; IOP was measured hourly for 8 hours the day before treatment and on the first and last treatment days. Pre-treatment mean IOP of the glaucomatous cats was 29.2 ± 15.2 mmHg vs 15.3 ± 3.8 mmHg in normal cats (PMC full text). The full text states: 'no effort was made to mask the observer or randomize the eye treated' — the right eye was always the treated eye.
Result: In PCG cats, mean IOP was significantly lower in treated vs control eyes for up to 8 hours following a single latanoprost treatment, and a maximal IOP reduction of 63% (relative reduction, as stated in the record) occurred in treated eyes at 3 hours; against the same time points in the pre-treatment phase, IOP was significantly lower at 3 and 4 hours, a mean reduction of 16 mmHg, or approximately 33% relative (PMC full text). Over extended treatment, however, there were no statistically significant changes in weekly mean peak IOP or maximum IOP fluctuation between treated and control eyes in normal or glaucomatous cats during any week, and no tendency for IOP to be reduced over time; after 3 weeks, treated eyes were still significantly lower than control eyes at 2–6 and 8 hours on the last treatment day, with the maximal effect at 4 hours. Latanoprost caused miosis in treated eyes of all cats, with rebound mydriasis at 24 hours post-treatment. The authors conclude latanoprost acutely lowered IOP in cats with PCG, that the effect appeared to diminish over 3 weeks, and that further research is needed on long-term IOP-lowering suitability.
Watch out: Only 6 glaucomatous cats, all with inherited congenital glaucoma — this record says nothing about the secondary glaucomas that make up much of feline practice. Eye allocation was fixed (right eye always treated) and the observer unmasked, so this card alone is design class (c). One glaucomatous cat received rescue dorzolamide during the pre-treatment phase for IOP above 60 mmHg. The headline's two percentages measure different things — 63% is the maximal reduction relative to the control eye at 3 hours on day 1, 33% (16 mmHg) is the mean reduction against pre-treatment at 3–4 hours — and neither is a sustained mean-IOP effect, which the weekly data explicitly did not show.
McDonald JE, Kiland JA, Kaufman PL, Bentley E, Ellinwood NM, McLellan GJ. Effect of topical latanoprost 0.005% on intraocular pressure and pupil diameter in normal and glaucomatous cats. Vet Ophthalmol. 2016;19 Suppl 1:13-23. PMID: 26183373. Registry ID: none in the record. MeSH: Animals · Aqueous Humor/drug effects · Cat Diseases/drug therapy* · Cats · Female · Glaucoma/congenital/drug therapy/veterinary* · Intraocular Pressure/drug effects* · Latanoprost · Ophthalmic Solutions/adverse effects/therapeutic use* · Prostaglandins F, Synthetic/adverse effects/pharmacology* · Pupil/drug effects*
Yang 2026: in 5 congenital-glaucoma cats, latanoprost lowered mean IOP by 5.5 mmHg vs saline controls at 4 hours (28.4% relative reduction, p < .001) — an effect the authors state was not clinically significant
Masked, controlled crossover study with randomized eye allocation (record's own wording; the full text qualifies the masking — observers were masked to the test drug administered but could not be masked to the treated eye, because of the known miotic effect of ophthalmic prostaglandin analogs in cats; publication types: Journal Article, Randomized Controlled Trial, Veterinary)
Who: Cats: 5 normal cats and 5 cats with feline congenital glaucoma (FCG) in a masked, controlled crossover study: a 1-day pre-treatment phase, then two 10-day treatment phases each followed by a 10-day recovery phase, in which all cats received twice-daily latanoprost 0.005% (LAT) or latanoprostene bunod 0.024% (LBN) in a randomized eye, with the contralateral eye serving as a saline-treated control; after recovery the same eye was treated with the opposite drug. IOP and pupil diameter were measured three times daily in all phases.
Result: Neither drug significantly reduced IOP in normal cats. In FCG cats, statistically significant reductions in mean IOP relative to controls were observed 4 hours after treatment for both LAT (−5.5 mmHg, 95% CI −8.4 to −2.5, p < .001) and LBN (−7.2 mmHg, 95% CI −10.2 to −4.3, p < .001); these represented 28.4% and 37.9% relative IOP reductions respectively, and the reduction was significantly greater with LBN than LAT by 1.8 mmHg (p = .012). The authors state, however, that these IOP reductions were not considered clinically significant, and describe the hypotensive effect as transient. Both drugs similarly reduced pupil diameter in normal and FCG cats.
Watch out: Only 5 glaucomatous cats, all congenital glaucoma, and the significant latanoprost difference is at the single 4-hour time point — 'transient' is the authors' own characterisation, and they judged the size of the reduction not clinically significant despite p < .001. Randomisation here is at eye level within each cat (which eye received drug vs saline control), not randomisation of cats to treatment arms, and the study's primary comparison is latanoprostene bunod vs latanoprost; the latanoprost-vs-saline contrast carded here is its internal control comparison. Masking was partial for this contrast: the full text states observers were masked to which test drug was given but could not be masked to the treated eye, owing to prostaglandin-induced miosis, so the treated eye was identifiable against its saline control.
Yang VY, Eaton JS, Kiland JA, Koch KE, Oikawa K, Hetzel SJ, McLellan GJ. Effects of 0.024% latanoprostene bunod on intraocular pressure and pupil diameter in normal cats and cats with congenital glaucoma. Vet Ophthalmol. 2026;29(1):e13302. PMID: 39609901. Registry ID: none in the record. MeSH: Animals · Cats · Intraocular Pressure*/drug effects · Cat Diseases*/drug therapy/congenital · Latanoprost*/therapeutic use/administration & dosage · Glaucoma*/veterinary/drug therapy/congenital · Cross-Over Studies · Female · Male · Pupil*/drug effects · Prostaglandins F, Synthetic*/therapeutic use/administration & dosage/pharmacology · Ophthalmic Solutions · Antihypertensive Agents*/therapeutic use/administration & dosage/pharmacology
Synthesis: latanoprost transiently lowers IOP for hours in congenital-glaucoma cats, with no sustained mean-IOP effect shown — POSSIBLE
Synthesis
Who: Synthesis of the two cards above (McDonald 2016, 6 glaucomatous cats; Yang 2026, 5 glaucomatous cats) and of the near-miss records documented in the result, fetched at drafting and deliberately not carded as claim-carriers.
Result: (1) Acute effect: both controlled glaucomatous-cat studies found a significant IOP fall within hours of a latanoprost dose — maximal 63% relative reduction vs the control eye at 3 hours (McDonald, day 1) and −5.5 mmHg (28.4% relative) vs saline controls at 4 hours (Yang). (2) Duration: McDonald's weekly data show no significant difference in mean peak IOP between treated and control eyes in any week and no tendency to reduction over time, and Yang's authors call the effect transient and not clinically significant — so a sustained pressure-lowering benefit, the thing glaucoma treatment needs, is not demonstrated. (3) Near-misses not carded: Studer 2000 (PMID: 11039551) gave latanoprost 0.005% once daily for 8 days to 9 healthy cats (with 14 dogs in the same record) and found feline IOP was not significantly affected while pupil diameter fell — healthy cats, not glaucoma, so it cannot carry a glaucoma claim, though it matches the carded studies' normal-cat arms. Park 2026 (PMID: 41047758) likewise studied 22 cats with NORMAL eyes, in which latanoprost-treated eyes, unlike omidenepag-treated eyes, showed no significant IOP reduction vs controls at 2–4 hours. A dexamethasone-induced ocular-hypertension study (PMID: 34369731) is an experimental hypertension model, not glaucoma, and its latanoprost subgroup is not carded. (4) Design class (a): Yang 2026 establishes randomisation (randomized eye) and masking for the latanoprost-vs-saline comparison in glaucomatous cats, answering this shelf's own comparison and population — with the flags on that card (eye-level randomisation, n = 5, and partial masking: observers were masked to the test drug but could not be masked to the treated eye, because of prostaglandin-induced miosis). McDonald 2016 is class (c) on its own by its full text's explicit statement. The POSSIBLE stamp reflects two small, consistent, congenital-glaucoma-only studies showing a real but transient effect.
Watch out: One-home check at drafting: none of PMIDs 26183373, 39609901, 11039551, 41047758 or 34369731 appears in any other pack on disk. Boundary honoured: shelf #328 is latanoprost in DOG primary angle-closure glaucoma — a different species whose strong canine results are never imported here; the feline evidence on this shelf is weaker and transient, and that species difference is the point of the shelf. Do not transport the congenital-glaucoma results to secondary feline glaucoma (uveitis- or neoplasia-associated), for which no carded record exists, and do not quote the 63% maximal relative reduction without the weekly mean-IOP null beside it.
Synthesis of McDonald JE et al. PMID: 26183373; Yang VY et al. PMID: 39609901; Studer ME et al. PMID: 11039551; Park SE et al. PMID: 41047758; PMID: 34369731. Registry IDs as on the individual cards (none in the records).
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