Abstract
Purpose::
To directly compare the ocular anti-inflammatory activity of amfenac with its prodrug nepafenac in a rabbit model. Although comparative anti-inflammatory studies have been reported comparing nepafenac with other NSAIDs such as diclofenac, few if any have compared its activity with amfenac, the active molecule.
Methods::
Amfenac (0.1% solution) was directly compared with its prodrug nepafenac (0.1% suspension) along with reference standards, ketorolac 0.4% and diclofenac 0.1%. Drugs (or vehicle) were administered in 2 single doses (50 µl/dose) to New Zealand white rabbits. Endotoxin (LPS, 10 µg/ml) was administered i.v. to induce ocular inflammation along with fluorescein isothiocyanate-dextran (FITC-dextran, M.W. = 70,000). Ninety minutes later, rabbit eyes were scanned using fluorophotometry, and aqueous humor PGE2 concentrations were obtained by immunoassay.
Results::
Aqueous humor FITC-dextran and PGE2 concentrations increased several fold following systemic LPS. Both amfenac and nepafenac resulted in nearly complete inhibition of FITC-dextran accumulation in the anterior chamber (97.4 % vs. 96.3% I, respectively). To a lesser extent, amfenac and nepafenac similarly inhibited PGE2 concentrations (68.0% vs. 62.0% I, respectively). The inhibition observed with amfenac and nepafenac on PGE2 levels is less than that observed with ketorolac (97.6% I) and slightly greater than that of diclofenac (62% I).
Conclusions::
Amfenac has ocular anti-inflammatory activity equal to or greater than its prodrug nepafenac in rabbit model, and has the advantage of being water soluble. From this study, it was not possible to discern any advantage of using a prodrug nepafenac over the active drug amfenac.
Keywords: inflammation • drug toxicity/drug effects • aqueous