Development and Evaluation of Nanoemulsions for Phenytoin Drug Loading

Aims: To understand about the nanoemulsion types and the process formation of spontaneous emulsification method by phase inversion. Then to test the different combinations of Oil, Surfactants and Co-surfactants for formation of suitable nanoemulsions for phenytoin drug loading.

Study Design: Spontaneous emulsification method by phase inversion used to form the nanoemulsions.

Place and Duration of Study: Department of Pharmaceutical Sciences, Kumaun University, Nainital, Uttarakhand, India.

Methodology: Phenytoin is a widely used drug in anticonvulsants class for epilepsy which comes under BCS Class II of drug category. Phenytoin has high permeability property but it also shows low solubility property which makes it difficult to absorb from GI tract hence make a poor penetration into the brain to target disease in the CNS. To overcome the situation of poor delivery of phenytoin, the requirement of nanoparticulate drug delivery as an innovative and effective drug delivery system from nose to brain raised. The objective of our study was to find the best combination of oil and Smix (surfactant and co-surfactant mixture) to form o/w (Oil in Water) nanoemulsions suitable for loading phenytoin drug using spontaneous emulsification method for brain targeting.

Results: Based on different compositions of oil (sunflower), surfactants (Tween-20), and co-surfactants (Transcutol P), forty-five test mixtures were made, water titration technique was employed for preparing the pseudo-ternary-phase diagrams. On the basis of these phase diagrams twenty-five phenytoin loaded nanoemulsions were formulated and further examined. After physicochemical characterization of these formulations the viscosity, pH, RI and % transmittance was found (6.149 ± 0.084 to 9.114 ± 0.027), (6.546 ± 0.018 to 6.656 ± 0.017), (1.395 ± 0.003 to 1.41 ± 0.005) and (94.53 ± 1.4% to 95.58 ± 1.2%) respectively. The release rate of phenytoin was found very satisfactory i.e., 98.51 ± 0.25 % to 99.82 ± 0.28 % after 24 hrs. The four formulations showed best release rate had further taken for particle size analysis. The particle size analysis showed that all the properties were in the desired range i.e., droplet size (18.9 to 21.9), zeta potential (-12.4 to -28.8), PDI (0.334 to 0.363). The study shows that the phenytoin loaded nanoemulsion is possible to make by water titration method and shall have a good drug release rate.

Conclusion: The nanoemulsion formulations passed through stress testing had also showed good release rate of phenytoin. Also, the other parameters like viscosity, pH, RI and percentage transmittance were in a quit satisfactory range to proceed further with these formulations. The particle size analysis confirms the formation of nanoemultions which had very good drug release rates.