Phase III latanoprost studies in Scandinavia, the United Kingdom and the United States

Three large, masked, multicenter studies are reviewed comparing the safety and efficacy of 0.005% latanoprost eyedrops given once daily to 0.5% timolol eyedrops given twice daily for six months in patients with elevated intraocular pressure (IOP). A total of 829 patients were recruited from centers in Scandinavia, the United Kingdom (UK) and the United States of America (USA). In addition, data are reviewed from the first 198 of these patients to complete an additional six months of latanoprost treatment in an open-label study. In all centers, both latanoprost and timolol were very effective in reducing the diurnal IOP. In the UK, both drugs reduced the IOP by 34%. In the USA, latanoprost was more effective than timolol, reducing IOP by 27% compared to 20%. In Scandinavia, latanoprost was given for three months in the evening and for three months in the morning while timolol was given twice daily for six months. Latanoprost given in the evening reduced IOP (35% reduction) significantly (p < 0.001) more than latanoprost given in the morning (31% reduction) and timolol given twice daily (27% reduction). Darkening of the iris color occurred in 7% of eyes treated with latanoprost for six months. A clinical evaluation of eyes with increased pigmentation, as well as preclinical studies, suggest that this side effect is a cosmetic problem in patients treated unilaterally. Other side effects were slight and not clinically significant. After one year of treatment with latanoprost in 198 patients, the IOP reduction of 32% was maintained. There was no loss of efficacy and no significant increase in the incidence of side effects or adverse events other than iris color darkening, which occurred or was suspected in 12%. These results demonstrate that latanoprost is a valuable drug for the treatment of chronic open angle glaucoma.