Use of factorial design in formulation and evaluation of ophthalmic gels of gatifloxacin: Comparison of different mucoadhesive polymers

The aim of this research was to develop different ophthalmic gels of gatifloxacin using mucoadhesive polymers. To improve intraocular delivery of topically applied drugs such as gatifloxacin, gel formulations were prepared since solutions have a shorter ocular residence time because of tear turnover. A 3(2) factorial design was used to investigate the combined effect of two independent formulation variables in the preparation of the gels. Nine batches were prepared as per experimental design and evaluated for gelation temperature, gel strength, bioadhesion, viscosity, permeation, and antimicrobial efficacy. A surface plot was also created to graphically represent the effect of the independent variables on the evaluation parameters. Drug polymer compatibility was evaluated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The prepared gels were observed to have a satisfactory gelation temperature, gel strength, and bioadhesion. Rheological study of the formulations indicated that gels exhibited pseudoplastic rheology. A modified device was used to evaluate drug permeation through a sheep's corneal membrane. In vitro permeation studies showed that a Peppas model was the best-fit model. Antimicrobial studies also indicated efficacy comparable to that of a marketed formulation. This systematic approach to formulation design should help in investigating the effect of variables in formulation processing.