Complications of opiate pharmacotherapy

Opioid therapy, both short- and long-term, has potential adverse effects related to: (1) occupancy of opioid receptors in the nociceptive system: analgesia (antinociception), biochemical tolerance, physical dependence and hyperalgesia; (2) occupancy of other opioid receptors—gastrointestinal slowing/constipation, nausea and vomiting, respiratory depression, pruritus, reward behaviors, immunosuppression; (3) effects on cognitive and psychomotor function, sleep; (4) metabolic by-products (morphine-6-glucuronide, normeperidine); (5) drug interaction, especially with other centrally active agents; (6) method of delivery; and (7) social and legal factors. Management of complications is based on: (1) dose reduction of opioid; (2) optimization of adjuvants; (3) symptomatic management of adverse effects; (4) opioid rotation; and (5) switching route of administration.