Transdermal patches of lidocaine/aspirin ionic liquid drug-loaded gelatin/polyvinyl alcohol composite film prepared by freeze-thawed procedure

The objectives of this study are to prepare a 5 wt% lidocaine/aspirin ionic liquid drug-loaded gelatin/polyvinyl alcohol composite film using a freeze-thaw procedure and to evaluate their physicochemical characteristics, in vitro drug release, and stability. Lidocaine/aspirin ionic liquid drugs can be prepared by an ion-pair reaction between the hydrochloride salts of lidocaine and the sodium salts of aspirin, which showed a significant change in their thermal properties when compared to those pure drugs. The results showed that a transdermal patch could feasibly be used in pharmaceutical transdermal patches with good physicochemical properties. A chemical interaction between the drug and polymer base was not found. Decomposition of the lidocaine/aspirin ionic liquid drug was found in the patch; however, the properties of the patch were not changed after drug loading. The patch controlled the drug release and showed good stability during the studied period of three months when kept at 4°C more than at ambient temperature and 45°C.