Vitreous and aqueous concentrations of brimonidine following topical application of brimonidine tartrate 0.1% ophthalmic solution in humans.

PURPOSE

To determine the vitreous and aqueous concentrations of brimonidine after topical application of the ophthalmic solution 0.1%.

METHODS

The prospective observational case series included patients with an idiopathic epiretinal membrane or macular hole who were scheduled for a pars plana vitrectomy. Brimonidine tartrate ophthalmic solution 0.1% was topically administered twice daily for 1 week preoperatively. Vitreous and aqueous humor was collected before vitrectomy, and then, the brimonidine concentration was measured with liquid chromatography tandem spectrometry (LC/MS/MS).

RESULTS

Twenty-four patients (19 phakic eyes and 5 pseudophakic eyes) were enrolled. The mean concentrations in the aqueous humor and vitreous were 336.0 ± 276.2 and 4.8 ± 3.2 nM, respectively. A significant relationship was observed between the vitreous and aqueous samples (P = 0.034, R(2) = 0.22). Nineteen (79%) of the 24 eyes showed more than 2 nM of brimonidine tartrate concentration in the vitreous. In the phakic eyes, the mean concentration of brimonidine in the vitreous was 4.9 ± 3.3 nM, while the mean concentration in the pseudophakic eyes was 4.1 ± 2.4 nM, demonstrating no significant difference between pseudophakic and phakic eyes (P = 0.59).

CONCLUSIONS

After 1 week of dosing, in most of the patients who topically received brimonidine tartrate 0.1%, the concentration in the vitreous of the molecule was above 2 nM, which is known to activate neuroprotective α-2 receptors in animal retina. The drug penetration into the vitreous seems to be independent of lens status.