FLUPIRTINE IS A UNIQUE CENTRALLY-ACTING, NON-OPIOID ANALGESIC WITH MUSCLE RELAXANT AND NEURO PROTECTIVE PROPERTIES. THE DRUG HAS MINIMAL TO NO AFFINITY FOR OPIOID RECEPTORS, AND ANALGESIA IS NOT MEDIATED VIA OPIOID MECHANISMS. ANALGESIC EFFECTS OF FLUPIRTINE HAVE NOT BEEN ANTAGONIZED BY NALOXONE. SEROTONERQIC MECHANISMS ALSO DO NOT APPEAR TO BE INVOLVED. THE ANALGESIC EFFECTS OF FLUPIRTINE APPEAR TO BE DOSE-RELATED. ACTIVATION OF THE NERVE CELL MEMBRANE IS REDUCED; THE NEURON IS LESS EXCITABLE. FLUPIRTINE INDIRECTLY ACTS AS N-METHYL-D-ASPARTATE(NMDA)- ANTAGONIST. FLUPIRTINE ALSO HAS A MUSCLE-TONE NORMALIZING EFFECT ASSOCIATEDWITH THE INHIBITION OF NEURONAL TRANSMISSION TO MOTOR NEURONS AND THE RESULTING ACTION ON INTERNEURONS; THIS IS NOT A GENERAL MUSCLE-RELAXING EFFECT BUT PRIMARILY AN EFFECT LOOSENING MUSCLE TENSENESS. FLUPIRTINE NORMALISES MUSCULAR TONUS WITHOUT AFFECTING THE MUSCULAR STRENGTH. TOLERANCE TO THE ANALGESIC EFFECTS OF FLUPIRTINE HAS NOT BEEN REPORTED DURING CHRONIC USE.