Formulation Development, Optimization and Characterization of Lidocaine Topical Patch

Abstract

The most common chronic complication of herpes zoster (causative agent varicella-zoster virus) is postherpetic neuralgia, in which peripheral neurons discharge spontaneously, having lowered activation thresholds and exhibit an exaggerated response to stimuli. Pain that persists for longer than one to three months after resolution of the rash is generally accepted as the sign of postherpetic neuralgia which occurs mainly in older patients. To overcome the problem of partial pain relief, less patient compliance and tolerability in available traditional treatments, Lidocaine topical patch was formulated by solvent casting method. Absorption study of Lidocaine with various liners and backing films was performed and from the study release liner Saint Gobain 8310 and Backing film EW 9100 was selected due to their less absorption of Lidocaine compared to other release liners and backing films. The topical patches were prepared using Aqueous Gelva as pressure sensitive adhesive, Oleyl Alcohol as a permeation enhancer, talc as a matrix stiffener, Glycerine as a smoothing agent, and Tween 80 as a surfactant. Optimized batch indicated 99.61% drug content, 1.24±0.11% moisture uptake, 1.42±0.19% moisture content, 4.56±0.17 N/inch Peel adhesion at 180˚ angle, 1.58±0.1 N/18.89mm² Tack property, 43±4.3 min Shear strength, 27.4±1.1 gf/inch Release force, 98±2.3% Drug Release. Cumulative permeation (57.39±10.31μg/cm²) & Skin Flux (5.58±1.00 μg/cm²/hr) of lidocaine topical patch was similar to innovator cumulative permeation (55.72±6.84 μg/cm²) & skin flux (5.42±0.66 μg/cm²/hr) through human cadaver skin after 12 hours ex-vivo permeation study. The selected formulation was found to be stable at 45˚C/75% RH after one month. Thus, it can be concluded that topical patch of Lidocaine was developed with similarity to the innovator and provides better healing compared to marketed oral formulation product.