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 alpha(2)-receptors.