Intraocular penetration and systemic absorption after topical application of dexamethasone disodium phosphate

To study the dexamethasone concentration in aqueous humor, vitreous, and serum of patients after repeated topical application of dexamethasone disodium phosphate.Prospective nonrandomized comparative trial.Twenty phakic patients scheduled for a first vitrectomy.All participants received dexamethasone disodium phosphate drops according to an application schedule intended to result in steady-state drug concentrations. Starting on the preoperative day, they received 1 drop of dexamethasone disodium phosphate (0.1%) every 1 hours until the time of vitrectomy (total, 10 or 11 drops). At night, ointment containing dexamethasone (0.3 mg/g) and gentamicin (5 mg/g) was administered once. From 7 AM on, the drop application schedule was resumed. At the start of the vitrectomy, samples were taken from the aqueous humor, vitreous, and blood.The dexamethasone concentrations in the aqueous humor, vitreous, and serum measured by radioimmunoassay.The mean dexamethasone concentrations in the aqueous humor, vitreous, and serum were 30.5 ng/ml (range, 7.1-57.7; standard deviation [SD] 15.0), 1.1 ng/ml (range, 0.0-1.6; SD 0.4), and 0.7 ng/ml (range, 0.0-1.2; SD 0.4), respectively.Compared with previously tested administration routes (peribulbar or subconjunctival injection or oral administration), the penetration of dexamethasone into the vitreous after repeated drop application is negligible. Despite the frequent dosing schedule, the dexamethasone concentration in the aqueous humor is far lower than after a subconjunctival injection with dexamethasone disodium phosphate. Systemic uptake is low.