Formulation and Evaluation of Film Forming Solution of Diphenhydramine Hydrochloride for Transdermal Delivery

Aim: The present work intends to formulate and evaluate film forming solution of diphenhydramine. Materials and Methods: Film forming solutions (FFS) for transdermal delivery of Diphenhydramine HCl were prepared using different polymers (hydroxypropyl cellulose, Eudragit L 100, polyvinylpyrollidone K30 and polyvinylpyrollidone K90), PEG 400 as plasticizer and ethyl alcohol as solvent. Results: The film forming solutions were found to display an acceptable drying time ranging from 2 to 5 min. In-vitro release studies indicated percentage drug released by the end of 8 h from FFS of HPC-EF, Eudragit L 100 and PVP K 30 was found to be 41.31 ± 2.1%, 14.81 ± 1.2 % and 25.7 ± 1.9 % respectively. FFS of HPC-EF that readily released drug were considered for further development by incorporating penetration enhancers like azone, isopropyl myristate and oleic acid. Steady state flux of drug across shed snake skin used as a barrier in vertical Franz diffusion cell was found to be 42.27 ±3.5 mg/cm2/hr, 51.18 ±4.9 mg/cm2/hr and 57.91 ± 7.2 mg/cm2/hr for FFS containing isopropyl myristate, oleic acid and azone as permeation enhancers respectively. Conclusion: Considering the plasma clearance of the drug and transdermal steady state flux, it can be inferred that FFS containing azone as enhancer needs to be spread across an application area of 0.5 cm2 to elicit a therapeutic response.