Pharmaceutically acceptable salts containing local anesthetic and anti-inflammatory activities and methods for preparing the same

Abstract

The present invention provides pharmaceutically acceptable salts having local anesthetic and anti-inflammatory activities. The preferred pharmaceutically acceptable salt is a diclofenac salt of lidocaine. Diclofenac is a non-steroidal anti-inflammatory drug ('NSAID'). Lidocaine is a local anesthetic. Other NSAID (except the salicylic acid derivatives of NSAID) can be used to replace diclofenac and/or other local anesthetics can be used to replace lidocaine. The pharmaceutically acceptable salts are crystalline compounds, which are distinctively different from either the NSAID alone or the local anesthetic alone, as indicated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), High Performance Liquid Chromatography (HPLC) and Fourier-Transformed Infrared Spectroscopy (FTIR) analyses. These pharmaceutically acceptable salts are suitable for use in topical treatment or parenteral injection to treat patients with localized pain, including muscle pain, joint pain, pain associated with herpes infection, and wound pain (such as surgical wound, burn wound etc.).