The effects of timolol maleate gel formulation 0.1% on intraocular pressure and pulse rate in dogs

The objectives of new topical formulations for the treatment of glaucoma are to reduce the intraocular pressure (IOP) and minimize the occurrence of side effects. The aim of this study was to determine the effects of topical application of timolol maleate gel formulation 0.1% applied once daily, on the intraocular pressure and pulse rate in ten healthy dogs. A clinical blinded trial was performed over two different periods; each period was divided into a pretreatment phase (D0) and four days of treatment (D1-4), with a wash out period of 10 days. Treatments consisted of administration of one drop of timolol 0.1% gel formulation once a day and artificial tears. The IOP and PR values were recorded in all animals five times daily (7:00 AM, 10:00 AM, 1:00 PM, 5:00 PM, and 9: 00 PM). Adverse events (conjunctival hyperemia, discomfort, breathing, and allergic reaction) were documented. Compared with the placebo treatment, the topical treatment with timolol gel formulation resulted in a significant decrease in IOP and PR. Already 24 hours after administration, TMG induced a significant reduction in IOP. In the group treated with TMG the mean decrease in IOP was 3.4 mm Hg (P<0.01), the mean decrease in PR was 10.8 (P<0.01). Topical administration of timolol maleate gel 0.1% formula was effective in lowering IOP in healthy dogs. The gel formulation improves bioavailability, but it seems there was no reduction in adverse cardiopulmonary effects.