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Topical 0.1% dexamethasone(50 microl) instilled QID in glaucomatous Beagles increased intraocular pressure (IOP) by about 5 mm Hg within the first seven to ten days in a four week test. The elevated levels of IOP persisted until drug instillations ceased. Both drug eye and placebo eye IOP levels were increased significantly over the predrug (control) IOPs. Comparisons of the IOP changes associated with topical dexamethasone in beagles bred for glaucoma and less than seven months of age to older glaucomatous Beagles did not detect any significant differences. The magnitude of elevation in IOP in both age groups was about 4.8 mmHg. During the week after cessation of the topical dexamethasone instillations, IOPs of both the drug and placebo eyes declined toward predrug levels. Primary open angle glaucoma in the Beagle exhibits a significant and rapid elevation in IOP following unilateral or bilateral 0.1% dexamethasone instilled QID.

Single doses (50 microliters) of 1% and 2% pilocarpine, instilled by a buffer-tip droptainer resulting in an approximate pH 7.0 solution, and 1, 2, and 4% pilocarpine, instilled by the standard droptainer, resulting a pH 5.0 solution, were evaluated in the glaucomatous Beagle model. Pupil size and intraocular pressure measurements were performed at 0, 1/4, 1/2, 3/4, 1, 2, 4, 6, and 8 hours. Signs of topical irritation (blepharospasm, conjunctival hyperemia and chemosis, and any corneal changes) were also monitored. Both solutions produced similar onset and duration of miosis and ocular hypotension, but the pH 5.0 solutions produced a brief elevation in intraocular pressure during the first hour post-drug instillation. Moderate blepharospasm, conjunctival hyperemia, and chemosis occurred with only the pilocarpine solutions with pH 5.0.