PURPOSE: This study compared the intraocular pressure (IOP)-lowering efficacy of 2 fixed combination products, brinzolamide 1%/timolol 0.5% suspension (Azarga, Brinz/Tim) and dorzolamide 2%/timolol 0.5% solution (Dorz/Tim), in patients with open-angle glaucoma or ocular hypertension who required a change in therapy due to elevated IOP while receiving IOP-lowering medication. METHODS: This was a one-year, multicenter, randomized, double-masked, active-controlled, parallel-group trial of Brinz/Tim and Dorz/Tim. IOP assessments were taken at 8 and 10 AM at week 2 and months 3 and 9, and at 8 AM, 10 AM, and 4 PM at months 6 and 12. Primary efficacy was a noninferiority comparison of mean IOP at the three month 6 time points. RESULTS: Of the 437 patients enrolled, 220 dosed Brinz/Tim whereas 217 dosed Dorz/Tim twice daily. Brinz/Tim produced IOP-lowering efficacy comparable to Dorz/Tim, with the upper 95% confidence limits for the differences between groups within +1.5 mm Hg at all assessment times, including the month 6 primary efficacy time points, establishing noninferiority. Differences in means numerically favored Brinz/Tim at 9 of 12 study visits and times. The IOP reductions ranged from 7.2 to 9.2 mm Hg for Brinz/Tim and from 7.4 to 8.9 mm Hg for Dorz/Tim. Although a similar overall safety profile was observed between the 2 treatment groups, Brinz/Tim showed significantly less ocular irritation (2.7% vs. 10.6%; P=0.0009) than Dorz/Tim. CONCLUSIONS: Brinz/Tim suspension provides statistically significant and clinically relevant IOP-lowering efficacy that is noninferior to Dorz/Tim. Additionally, Brinz/Tim affords an ocular comfort advantage compared with Dorz/Tim.