Treatment for glaucoma, a common ocular disease in dogs, includes topical ophthalmic solutions that decrease intraocular pressure (IOP) and pupil diameter (PD). Dose-response studies conducted in normal dogs and beagles with inherited glaucoma were used to establish concentrations that maximize therapeutic response. In this study, 4 concentrations (0.0033%, 0.001%, 0.00033%, 0.0001%) of travoprost (Travatan, alcon.com) were used q24h in 12 glaucomatous beagles. Dogs were randomly assigned to a treatment group and the right eye was treated with travoprost; the left eye was a control. After a 7-day washout period, the left eye was treated and the right eye was the control. IOP and PD were measured before and at 3, 6, and 24 hours after installation. This study found that all but the 0.0001% concentration of travoprost significantly lowered IOP and PD, including the 0.00033% concentration, which is one-twelfth the concentration of the commercial product (0.004%).

Commentary
Topical prostaglandins have been the choice drug for primary glaucoma treatment in veterinary medicine. The type of glaucoma (primary/secondary) and further classification of primary glaucoma (open-angle/angle-closure) are equally important for drug selection and management. The glaucomas are not just a single disease, much less requiring a single therapeutic drug regimen. Species and individual aqueous humor dynamics have impact on drug effectiveness. In this study, concentrations of travoprost as low as 0.00033% decreased IOP at early time points, but when managing primary glaucoma, maintaining low stable IOPs with fewer fluctuations throughout the circadian IOP cycle is critical. This was only partly achieved with the 0.0033% concentration. In addition, the concentrations evaluated are not commercially available. Travoprost 0.004% may be more expensive than other equally effective and well studied PGF2 derivatives (eg, latanoprost).—Cherlene Delgado, DVM

Source
Dose response for travoprost in the glaucomatous beagle. MacKay EO, McLaughlin M, Plummer CE, et al. VET OPTHALMOL 15:31-35, 2012.