Preemptive analgesia.

Preemptive analgesia describes a situation where the administration of a pharmacological agent administered before the onset of a painful stimulus causes a decrease in the intensity of pain felt, and subsequently there is a decrease in the total amount of analgesic required compared with the administration of an agent after a painful stimulus. It is best understood if it is thought of as a block to afferent impulses that are trying to reach the central nervous system before a tissue injury. Preemptive analgesia, administered in the form of narcotics, nonsteroidal antiinflammatory agents, or local anesthetics, is thought to alter peripheral and central sensitization to nociceptive impulses.