FACTORIAL DESIGNS IN OPHTHALMIC FORMULATION DEVELOPMENT OF ENALKIREN

Abstract A formulation development approach for ophthalmic solutions using a 2 3 factorial design is presented. Enalkiren (ABBOTT-64662), a renin inhibitor, has been shown to lower intraocular pressure in rabbits and monkeys. The influence of pH, presence of EDTA and the addition of PVP K90 to solutions of Enalkiren for ophthalmic use was investigated in rabbit. Results indicated that pH had a significant effect on the aqueous humor levels of Enalkiren after application to the rabbit eye. Additionally, interaction effects between PVP and pH were identified. It was demonstrated that aqueous humor levels of Enalkiren could be increased by an average of 50% by adding 4% PVP K90 to a pH 7 formulation. The application of a factorial design study may be useful in the evaluation of variables that influence the in vivo performance of ophthalmic formulations.