Breakthrough pain in cancer patients.

Breakthrough pain is a transient exacerbation of pain that occurs either spontaneously or in relation to a specific predictable or unpredictable trigger, despite relatively stable and adequately controlled background pain. A typical episode of breakthrough pain has a fast onset and short duration, yet despite the self-limiting nature of each breakthrough pain, the repeated episodes can have a significant effect on patients' quality of life. Normal-release oral opioids have been the mainstay pharmacological approach for patients who are receiving an around the clock opioid regimen, but the onset and duration of action of oral opioids such as morphine may not be suitable for treating many breakthrough pains. Efforts to provide non-parenteral opioid formulations that could provide more rapid, and more effective, relief of breakthrough pain have led to the development of transmucosal opioid formulations.