Evaluation of lidocaine loaded clay based dermal patch systems

Abstract

The objective was to evaluate anti-nociceptive activity of a novel clay based dermal patch system for potential use in first degree burn wounds. First, clay patches with silver were formulated for antisepsis. Subsequently they were loaded with 5 mg/cm2 of lidocaine. The skin penetration studies were performed to ensure the delivery of drug into the skin. Finally, the lidocaine loaded silver clay patches were screened for in-vivo anti-nociception using hot plate analgesiometer in rats. The lidocaine loaded silver clay patches did not show anti-nociception after 6hrs of application despite significant amount of drug release observed in in-vitro studies. To discover the reason for failure of the patch system in thermally induced pain model, mechanistic studies were performed using clay patches not loaded with silver colloid. When lidocaine loaded clay patches, devoid of silver were subjected to in-vivo evaluation, a significant anti-nociceptive activity was observed. The reason for masking of anti-nociceptive activity of lidocaine in the silver loaded patches was potentially due to coating of silver on the paw rendering the skin more conductive. Often, additional mechanistic studies are required to be performed to critically assess the in-vivo data.