[Interactions between opioids and local anesthetics at the level of the dorsal horn of the spinal cord].

For many years, local anaesthetic drugs, given spinally, have been used to control pain after surgery or during parturition. For nearly 20 years, we have known that opioids given by the same way have an analgesic effect. However the later group do not provide satisfactory analgesia in several pain contexts but also give troublesome side effects; local anaesthetics are associated also with side effects. Experimental and clinical studies have shown that the combination of local anaesthetics with opioids provides some degree of synergism, associated with a reduction of side effects. Further studies are needed to confirm the analgesic benefit and the potential decrease of side effects, but also to determine the minimal effective dose regimen in relation with the type of pain.