PURPOSE: To evaluate intraocular pressure (IOP) control over 24 hours using travoprost and timolol fixed combination (TTFC) administered in the morning or evening in primary open-angle and exfoliative glaucoma.METHODS: Patients were randomized to TTFC administered in either the morning or evening for 8 weeks. Previously treated patients underwent an untreated washout period of 4-6 weeks, after which baseline IOP was required to be > 25 mm Hg and < 38 mmHg (in two readings taken at 10.00 +/- 1 hours). During the treatment period, IOP was measured at 10.00, 14.00, 18.00, 22.00, 02.00 and 06.00 hours. Patients were then treated with the opposite dosing regimen for 8 weeks and IOP measurements were repeated.RESULTS: In 32 subjects who completed the study, the untreated baseline IOP following washout was 27.7 +/- 3.5 mmHg. Both dosing regimens reduced IOP from baseline at each time-point and throughout the 24-hour diurnal curve (p < 0.0001). When treatments were compared directly, evening dosing (18.4 +/- 3.3 mmHg) provided a statistically significant lower 24-hour curve than morning dosing (19.2 +/- 3.5 mmHg; p = 0.001). Evening dosing also resulted in a lower 24-hour IOP fluctuation (3.8 +/- 1.6 mmHg) than morning dosing (5.1 +/- 1.6 mmHg; p = 0.0002) and lower peak IOP (p = 0.0003).CONCLUSIONS: Both morning and evening administration of TTFC provide effective 24-hour IOP reduction, but evening dosing demonstrates better 24-hour pressure control.