Disclosed herein is a method for prolonging analgesic effect of a membrane permeable local anesthetic in a subject in need thereof. The method uses cinnamaldehyde as an adjuvant which, when administered prior to or simultaneously with the administration of a local anesthetic, prolongs the analgesic effect of the local anesthetic. Also disclosed herein is a method for providing analgesic effect in a subject in need thereof. The method uses cinnamaldehyde as an analgesic compound which, when administered alone to the subject in an analgesically effective amount, provides the analgesic effect.