Vitreous concentration of topically applied brimonidine tartrate 0.2%

To determine the vitreous concentration of brimonidine after topical administration of Alphagan.

Prospective observational case series.

Eighteen patients scheduled for elective pars plana vitrectomy.

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.

The concentration of brimonidine in human vitreous.

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.

Topically applied brimonidine results in vitreous levels at or above 2 nM, the concentration shown to activate alpha(2)-receptors.