Abstract Objectives To evaluate the fluctuations in 24 h mean intraocular pressure (IOP) when switching prostaglandin analogs in patients with glaucoma. Methods Fourteen patients with primary open angle glaucoma were evaluated with monthly 24-h IOP curves, using a monthly switching pattern of prostaglandin analogs and brinzolamide during 3 years of follow-up. Results Average IOP and average fluctuation (peak to through difference) were significantly higher with brinzolamide than with any of the analogs. There was no significant difference in either parameter with the different prostaglandin analogs, regardless of the order in which they were evaluated, or even if a month on brinzolamide was intercalated between the analogs. Conclusions Brinzolamide was less effective than prostaglandin analogs in reducing 24-h mean IOP and its fluctuations. Switching analogs had no significant effect on mean IOP or mean IOP fluctuations.