PURPOSE: To investigate the circadian and blood pressure (BP) reduction obtained with timolol maleate 0.5% solution administered twice daily versus timolol 0.1% in gel-forming carbomer administered in the morning in patients with primary open-angle glaucoma (POAG).METHODS: This investigator-masked, crossover study prospectively enrolled naive POAG patients not receiving systemic cardiovascular medications. Following a baseline evaluation, they were randomized to receive a timolol 0.5% solution or timolol 0.1% hydrogel for 2 months and then switched to the alternative medication for a further 2 months. Intraocular pressure (IOP) phasing (sitting Goldmann tonometry at 10 am, 2 pm, 6 pm, and 10 pm and supine Perkins tonometry at 2 am and 6 am) and ambulatory home BP monitoring were measured at baseline and after each treatment period.RESULTS: On the basis of a prospective sample size estimate, 28 patients were analyzed. Mean 24-hour IOP decreased from 23.1 ± 0.7 mm Hg at baseline to 18.9 ± 0.6 mm Hg after timolol 0.5% and 18.9 ± 0.8 mm Hg after timolol 0.1% hydrogel (P < .001); both formulations also significantly decreased diurnal, nocturnal, and individual time point IOP in a statistically similar manner. Systolic and diastolic BP remained generally unaffected. The calculated diastolic ocular perfusion pressure was either unaffected or tended to increase with either medication.CONCLUSION: Both timolol formulations show similar and significant circadian efficacy and have minimal effects on BP and calculated diastolic ocular perfusion pressure.