We had proved that dextromethorphan and its metabolites had sciatic nerve blockade, infiltrative cutaneous analgesia, and spinal anesthesia in rats. All of them are local anesthetics. Local anesthetics have been used in acute and chronic pain management for 100 years, but long-acting local anesthetics or suitable formulations are still not enough for clinical therapies. Therefore, our study will emphasize the interaction of drugs and long-acting effects of dextromethorphan and its metabolites on local anesthesia and neuropathic pain. This project will be carried out for three years. In the first year, combination of drugs (i.e. epinephrine or clonidine) with dextromethorphan, dextrorphan or 3-methoxymorphinan on the interaction or prolonging of the effect of infiltrative cutaneous analgesia, sciatic nerve blockade, and spinal anesthesia will also be determinated. In the second year, twenty-five oil dosage forms of local anesthetics will be formulated, and these formulations will be evaluated on infiltrative cutaneous analgesia and sciatic nerve blockade. In the last year, fifteen oil formulations will be evaluated on neuropathic pain.
