Purpose: To determine whether exposure of sodium fluorescein (NaF) to the choroid-retina region in the posterior segment of the eye is greater with suprachoroidal injection when compared to intravitreal and transscleral routes.
Methods: Suprachoroidal injection, a new approach for drug delivery to the posterior segment of the eye was validated using a 34 G needle and Indian ink injections in Sprague Dawley rats, followed by histology. Delivery of NaF was compared in Sprague Dawley rats after suprachoroidal, posterior subconjunctival, or intravitreal injections. NaF levels were monitored noninvasively up to 6 hours using Fluorotron Master™, an ocular fluorophotometer Pharmacokinetic parameters were estimated using WinNonlin.
Results: Histological analysis indicated localization of India ink to the suprachoroidal space below sclera, following injection. NaF delivery to choroid-retina was in the order: suprachoroidal > intravitreal >posterior subconjunctival injection. Peak NaF concentration (C(max)) in choroid-retina was 36-fold (p = 0.001) and 25-fold (p = 0.001) higher after suprachoroidal (2744±1111 ng/ml) injection when compared to posterior subconjunctival (76±6 ng/ml) and intravitreal (108±39 ng/ml) injections, respectively. NaF exposure (AUC(0-360min)) to choroid-retina after suprachoroidal injection was 6-fold (p = 0.001) and 2-fold (p = 0.03) higher than posterior subconjunctival and intravitreal injections, respectively. Choroid-retina T(max) was observed immediately after dosing with suprachoroidal injections and at 10 and 27.5 minutes, respectively, with subconjunctival and intravitreal injections.
Conclusions: Suprachoroidal injections are feasible in a rat model. Suprachoroidal injections resulted in the highest bioavailability, that is, the extent and rate of delivery of NaF to choroid-retina, when compared to intravitreal and posterior subconjunctival injections. Ocular fluorophotometry is useful for noninvasive monitoring of NaF in rats following administration by various routes including suprachoroidal route.