INHIBITION OF PILOCARPINE-INDUCED AQUEOUS-HUMOR FLARE, HYPOTONY, AND MIOSIS BY TOPICAL ADMINISTRATION OF ANTIINFLAMMATORY AND ANESTHETIC DRUGS TO DOGS

Objective-To investigate the mechanism by which pilocarpine causes inc reased aqueous humor (AH) flare, hypotony, and miosis in dogs. Animals -6 dogs with normal eyes. Procedure-Both eyes of each dog were treated topically with a 2% solution of pilocarpine, and 1 eye of each dog wa s additionally treated with commercially available ophthamic solutions . Breakdown of the blood-aqueous barrier (BAB) was quantitated in each eye, using laser flaremetry to measure AH flare. Intraocular pressure and pupil size were also measured. Results-Pilocarpine caused increas ed flare from BAB breakdown that was inhibited by the drugs tested. In hibition (most to least) of BAB breakdown was flurbiprofen more than d iclofenac, proparacaine, or suprofen, which were more than 0.125 or 1. 0% prednisolone. Inhibition appeared dose-dependent and caused consens ual inhibition in the contralateral eye. Intraocular pressure was decr eased only in proparacaine-treated eyes and increased in eyes treated with nonsteroidal anti-inflammatory drugs (NSAID). Flurbiprofen and pr oparacaine were the most effective at blocking miosis. Conclusions-Pil ocarpine produced a predictable, reproducible BAB breakdown in dogs. M iosis and increased AH flare were inhibited equally by proparacaine or NSAID, suggesting that these signs were caused by neuropeptide releas e into the AH from antidromic stimulation, which subsequently triggers prostaglandin production. Hypotony was inhibited only by anti-inflamm atory drugs. Clinical Relevance-Proparacaine in combination with piloc arpine would be the best choice for treating dogs with acute glaucoma. Topical administration of NSAID should not be used to treat dogs with acute glaucoma, because they increase intraocular pressure and negate the effects of pilocarpine.