Emerging techniques in the treatment of postoperative pain

Purpose. Causes of inadequate postoperative pain control, challenges with currently available analgesic therapies, characteristics of optimal postoperative analgesic therapy, a liposome-encapsulated, sustained-release dosage form of morphine, and other investigational analgesic therapies are described. Summary. Technical difficulties in analgesic drug administration, inappropriate prescribing, unfounded patient fears or expectations, and the lack of availability of parenteral dosage forms of certain analgesic agents can potentially contribute to inadequate postoperative pain control. The use of epidural catheters for analgesic therapy is limited by the use of prophylactic anticoagulation, the tendency for catheters to migrate and fail, and the need for nursing staff time to monitor the catheter site and infusion pump. Continuous peripheral blocks are not always effective, the devices used are bulky, and the technology is prone to failure. Multimodal therapies are labor-intensive, and some components must be given orally because they are not available in parenteral dosage forms. Optimal postoperative analgesic drug therapy would therefore be noninvasive, easy to administer, require no cumbersome equipment, cause no or minimal adverse effects, and be safe to use in patients receiving prophylactic anticoagulation. A new morphine sulfate sustained-release liposome injection has several of these characteristics, including ease of administration and compatibility with anticoagulation. Single-dose epidural administration of morphine sulfate sustained-release liposome injection in patients undergoing hip arthroplasty provided better pain control than i.v. opioid analgesics given by PCA, with similar adverse effects. Conclusion. Opioid analgesics remain the mainstay of postoperative analgesic therapy, but the development of infusion pumps with improved reliability; needle-free technologies, parenteral dosage forms of acetaminophen, selective cyclooxygenase-2 inhibitors, and other non-opioid therapies; and new opioid analgesic agents that provide analgesia without the adverse effects of currently available opioid analgesics may substantially improve postoperative analgesia and health-related quality of life in the postoperative pain patient in the future.