In vivo pharmacokinetics and in vitro pharmacodynamics of nepafenac, amfenac, ketorolac, and bromfenac

Purpose

To evaluate the aqueous humor concentrations and cyclooxygenase (COX) inhibitory activities of nepafenac, amfenac, ketorolac, and bromfenac after topical ocular administration of Nevanac (nepafenac 0.1%), Acular LS (ketorolac 0.4%), or Xibrom (bromfenac 0.09%).

Setting

Five private ophthalmology practices throughout the United States.

Methods

Patients requiring cataract extraction were randomized to 1 of 3 treatment groups: Nevanac, Acular LS, or Xibrom. Patients were administered 1 drop of the test drug 30, 60, 120, 180, or 240 minutes before cataract surgery. At the time of paracentesis, an aqueous humor sample was collected and later analyzed for drug concentration. In addition, COX-1 (homeostatic) and COX-2 (inducible) inhibitory activities of nepafenac, amfenac, ketorolac, and bromfenac were determined via the in vitro measurement of prostaglandin E₂ (PGE₂) inhibition.

Results

Seventy-five patients participated in the study. The prodrug nepafenac had the shortest time to peak concentration and the greatest peak aqueous humor concentration (C_max). The C_max of nepafenac was significantly higher than that of the other drugs (P<.05), including the higher-concentration ketorolac (0.4%). The area under the curve (AUC) of nepafenac was significantly higher (P<.05) than the AUCs of amfenac, ketorolac, and bromfenac. The combined AUCs of nepafenac and amfenac were the highest of all drugs tested (P<.05). Ketorolac showed the most potent COX-1 inhibition, whereas amfenac was the most potent COX-2 inhibitor. The PGE₂ aqueous humor levels of each study medication were highly variable; as a result, meaningful interpretation of the data was not possible.

Conclusion

Nepafenac showed significantly greater ocular bioavailability and amfenac demonstrated greater potency at COX-2 inhibition than ketorolac or bromfenac.