Current approaches to analgesic drug delivery for chronic pain.

A growing number of governmental and professional guidelines internationally have supported aggressive treatment of acute (e.g., postsurgical), cancer, and noncancer pain. The basis for such support is awareness that aggressive control of acute pain reduces postoperative complications and speeds recovery. Chronic noncancer pain (e.g., back pain, headache...) exacts enormous financial costs in each developed nation. Patients' quality of life and possibly even duration of survival as well as associated caregiver burden are enhanced by adequate pain control in patients with chronic pain due to cancer and noncancer causes. Because humanitarian benefits of pain control are supplemented by economic savings, a variety of techniques have been introduced to improve the temporal or spatial profiles of analgesic drug delivery. This brief survey describes the physiological basis for considering pain itself as a disease, the principal drugs and delivery approaches for treatment of severe pain, and the future of "combination analgesic chemotherapy".