Evaluation of multiple doses of 4 and 6% timolol, and timolol combined with 2% pilocarpine in clinically normal Beagles and Beagles with glaucoma

SUMMARY Topically applied 4% timolol, 4% timolol combined with 2% pilocarpine, 6% timolol, and 6% timolol combined with 2% pilocarpine were evaluated in clinically normal Beagles and Beagles with glaucoma. The drugs were instilled twice daily for 5 days. Changes in intraocular pressure (iop), pupil size, and heart rate were recorded on days 1, 3, and 5 at 0, 2, 5, and 8 hours, starting at 8:30 am. In clinically normal dogs, 4 and 6% topically administered timolol did not cause consistent reductions in iop; however, with addition of 2% pilocarpine, iop was consistently lower. In the Beagles with glaucoma, 4 and 6% timolol and, to a greater extent, 4 and 6% timolol combined with 2% pilocarpine lowered iop. The combinations lowered iop and reduced pupil size consistently. In all test groups, either 4 or 6% topically applied timolol caused approximately 10% decrease in mean heart rate.