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Role of anaesthetics and opioids in perioperative hyperalgesia: one step towards familiarisation.

Opioids produce analgesia. Nevertheless, clinical experience indicates that they may result in increased pain sensitivity, or, opioid-induced hyperalgesia. The development of opioid-induced hyperalgesia may involve an interaction between neuropharmacological facilitation and inhibition of pain, an abnormal neuroplasticity of the m opioid receptor system, an as yet unclear dysfunctional cellular recruitment within the brain and spinal cord centres, and sensitisation of pronociceptive pathways. Each or all of the above contribute to the establishment of a condition wherein pain appreciation is heightened despite the administration of opioids in appropriate doses and regimens.