Additive IOP-reducing effect of latanoprost in patients insufficiently controlled on timolol

Purpose: To evaluate the effect on intraocular pressure (IOP) of switching from timolol to latanoprost or adding latanoprost to timolol in patients with open angle glaucoma or ocular hypertension where IOP is not adequately controlled with timolol. Methods: This was a 6‐week, double‐masked, randomised multi‐centre study. 53 patients with primary open angle glaucoma, capsular glaucoma, or ocular hypertension with an IOP of at least 21 mmHg on current therapy were recruited. After a run‐in period of at least 2 weeks on timolol, 5 mg/ml twice daily, patients were randomised to one of three groups. One group continued on timolol, one switched from timolol to latanoprost, 50 μg/ml once daily, and a third group received latanoprost in addition to timolol. The efficacy was evaluated by comparing IOP at 9 AM at baseline and after 6 weeks of treatment. Results: IOP at baseline and after 6 weeks of treatment (mean±SEM) were 24.2±0.9 and 23.8±1.0 mmHg (n=16) for patients continuing on timolol, 26.3±1.2 and 19.6±1.1 mmHg (n=17) for patients switching to latanoprost, and 23.2±1.0 and 17.5±0.8 mmHg (n=17) for patients with combined treatment. Adding latanoprost to timolol reduced IOP with 5.9±0.9 mmHg (p<0.001) and switching from timolol to latanoprost reduced IOP with 5.0±0.9 mmHg (p<0.001), which caused in each group a significant IOP reduction of about 25%. Conclusions: The effect of latanoprost was additive to that of timolol, and a good effect on IOP reduction was also achieved by switching from timolol to latanoprost, suggesting that a switch in many patients is an effective alternative to combination treatment.