Preparation and Evaluation of Matrix Containing Lidocaine and Prilocaine for Using in Transdermal Films

Background: Lidocaine and prilocaine are amide-type local anesthetic agents that are expectedly adequate to create a rapid pharmacological effect immediately after using transdermal delivery system. 
Objective: The aim of this study was to investigate the effect of hydrophilic and hydrophobic materials on drug release from different polymeric films containing lidocaine and prilocaine. 
Materials and Methods: Several films containing lidocaine and prilocaine were prepared using ethyl cellulose (EC) or hydroxypropyl methylcellulose (HPMC) polymers. The effect of propylene glycol (PG) and polyethylene glycol 4000 (as permeation enhancers) and triacetin or dibutyl phthalate (DBP) as plasticizer on tensile strength, moisture absorption, content uniformity, and drug release properties were investigated. In vitro permeations studies were carried out using Fransz diffusion cells and samples were analyzed by highperformance liquid chromatography for each drug. 
Results: DBP unlike triacetin had a dramatic effect on drug release rate and moisture absorption in HPMC films. The presence of PG on the formulations containing EC caused an increase in the moisture absorption and drug release and shifted the mechanism of release from Fickian diffusion to Case-II transport. PEG4000 was not a significant effect on these variables in the HPMC films. 
Conclusion: Hydrophilic additives like PG when used in an water-insoluble membrane act as a channeling agent and increase the rate of drug release because in dissolution medium they dissolve out of the film and leave channels from which drug can be released more rapidly.