[Mechanism-based pharmacotherapy for cancer pain].

Cancer pain is usually treated by 1) pharmacotherapy, 2) nerve block, 3) radiation therapy, 4) cognitive therapy and 5) alternative medicine. Among these methods, pharmacotherapy is the simplest way to relieve cancer pain without special equipment or special settings. WHO cancer treatment guideline shows morphine is effective to most cancer pain. However, 10-20% of the patients' pain is refractory to morphine. A majority of such refractory pain is due to nerve injury caused by cancer itself or by treatment. Recently, many biological processes involved in the mechanism of neuropathic pain have been elucidated. Pharmacological treatment aimed at blocking such processes should produce specific effects on the pain. Such mechanism-based pharmacotherapy is the most effective way to treat difficult pain.