RESUMO
OBJECTIVE: To measure the magnitude and duration of the hypotensive effect of two prostaglandin analogues in glaucoma patients using the water drinking test (WDT). METHODS: Patients received latanoprost or travoprost every 24 h and then every 48 h. Untreated WDT were performed at 7 am and with treatment 12, 36 and 44 h after the last dose; intraocular pressure (IOP) peak, fluctuation and the difference between peak and isolated IOP measurements at consultation times were calculated. RESULTS: Forty-one eyes of 21 patients with primary open-angle glaucoma were included; 22 eyes received latanoprost, and 19 received travoprost. Mean untreated isolated IOP was 17.20 standard deviation (S.D.) 3.73 and 16.95 S.D. 2.61 mmHg and peak pressure 22.45 S.D. 2.91 and 21.58 S.D. 3.79 mmHg, for the latanoprost and travoprost groups, respectively. With treatment, peak pressure was reduced by 22.64% and 20.29% at 12 h, 18.44% and 14.64% at 36 h and 16.17% and 14.46% at 44 h, respectively. The fluctuation without treatment was 4.36 and 5.11 mmHg, and with treatment at 12 h was reduced to 2.77 and 2.89 mmHg, increasing again at 36 and 44 h. CONCLUSIONS: A hypotensive effect was evident up to 44 h after the last dose of latanoprost and travoprost, similar for the two drugs and decreasing over time. IOP fluctuation was only reduced at 12 h.