MICROEMULSION BASED GELS FOR TARGETING NEUROPATHIC PAIN

Background: Neuropathic pain is a type of chronic pain that occurs when nerves in the central nervous system become injured or damaged. Currently only a limited number of topical treatments are available to treat it. Hence an attempt was made to alleviate symptoms of neuropathic pain by topical application of a local anaesthetic drug.

Results: Microemulsions were formulated using Oleic acid as the oily phase and Tween 80 and ethanol in 1:1 ratio as the surfactant and cosurfactant respectively. The microemulsions thus formed were clear, transparent and aesthetic in appearance and showed low viscosity and near neutral pH. They exhibited electrical conductivity indicating they were o/w microemulsions. The particle size was in the submicron range while the polydispersity index was 0.4 indicating a uniform particle size distribution. A satisfactory and elegant gel was obtained using Xanthan gum as the gelling agent. In-vitro and ex-vivo drug diffusion indicated a sustained release of the drug over 8 hours. Anti-nociceptive activity was tested using hot plate and tail flick tests where the microemulsion based gels of Ropivacaine exhibited a marginally better efficacy as compared to the conventional Lidocaine gel.

Conclusion: Based on these findings, Ropivacaine can be used as a suitable local anaesthetic drug which acts topically in low doses and can provide significant pain inhibition when given as a microemulsion gel.