OPIOIDS - A PHARMACOLOGISTS DELIGHT

1. Opioids, in one form or another, have been used for their pain-reli eving properties from prehistoric times: they are still the first line medication for the treatment of severe nociceptive pain and are likel y to remain so for the foreseeable future. 2. The therapeutic index of opioids used for pain management is low: opioid side effects are esse ntially extensions of therapeutic effects and no available agent has a marked advantage over the others. When used for opioid 'anaesthesis', differences in therapeutic index are more obvious due to differences in non-opioid effects. 3. Opioid receptors in brain and spinal cord pe riphery are the main 'therapeutic targets' and clinical dosage strateg ies have been derived using a variety of systemic (indirect or blood-b orne) methods as well as intraspinal and intracerebroventricular (dire ct) methods: no method, however, is without potential side effects, Pe ripheral opioid effects are now being exploited with intra-articular i njection. 4. Opioid pharmacokinetics and pharmacodynamics are characte rized by high inter-subject variability: accordingly, patient-controll ed dosage strategies are found to be more successful for pain control than deterministic recipes.