Vitreous concentration of topically applied brimonidine tartrate 0.2

Abstract Objective To determine the vitreous concentration of brimonidine after topical administration of Alphagan. Design Prospective observational case series. Participants Eighteen patients scheduled for elective pars plana vitrectomy. Methods Brimonidine tartrate, 0.2%, was topically administered twice or three times daily for 4 to 14 days preoperatively in 13 patients. Four patients served as controls, without application of brimonidine. A dry, undiluted vitrectomy specimen obtained intraoperatively was collected, frozen, and sent to an independent bioanalytical facility for quantitative determination of vitreous concentration of brimonidine using gas chromatography/mass spectrometry. Main outcome measures The concentration of brimonidine in human vitreous. Results All patients treated with brimonidine measured above the lower limit of quantitation with a mean vitreous concentration of 185 ± 500 nM. All patients not treated with brimonidine measured at or below the lower limit of quantitation of 0.05 nM. There was a trend toward higher concentration in patients who were either aphakic or pseudophakic compared with those that were phakic. Conclusions Topically applied brimonidine results in vitreous levels at or above 2 nM, the concentration shown to activate α 2 -receptors.