Purpose: The aim of this study was to determine the vitreous brimonidine concentration of
topically applied brimonidine-Purite 0.15%.
Methods: Patients scheduled for a pars plana vitrectomy were invited to participate in this
study after institutional review board (IRB) approval was obtained. Each patient was asked
to apply brimonidine-Purite (0.15%) drops in the designated eye either every 12 h (b.i.d.; 9
patients) or every 8 h (t.i.d.; 10 patients) for the 2 weeks preceeding scheduled surgery. The
importance of the last topical dose being 12 h (b.i.d. group) or 8 h (t.i.d. group) before the
scheduled surgery, was emphasized. Four (4) patients served as controls and did not receive
any drops. Vitreous (∼0.5–1.0 mL) was aspirated prior to opening the infusion line. Specimens
were frozen at –68°C until analyzed.
Results: In the b.i.d. group, the mean concentration of brimonidine was 16.74 nM ± 10.33
standard deviation (range, 0.42–34.68 nM; median, 16.38); in the t.i.d. group, the mean concentration
of brimonidine was 19.16 nM ± 15.40 standard deviation (range, 0.22–39.48 nM; median,
16.98). A significant difference was observed between the (no drug) control vitreous brimonidine
levels and b.i.d. or t.i.d. vitreous levels (P < 0.01, <0.01, respectively; n = 4, 9, and
10, respectively); and in brimonidine levels between t.i.d. phakic patients and t.i.d. patients
with posterior chamber lens (P = 0.04; n = 4 and 6, respectively).
Conclusions: Brimonidine-Purite 0.15%, topically applied b.i.d. or t.i.d. for 2 weeks prior to
collection, acquired vitreous levels of brimonidine at or above the 2-nM concentration known to activate the neuroprotective alpha-2 receptor in animals.
