<qa>  What is the standard of care for breakthrough pain episodes?The purpose of this study is to evaluate the safety of BEMA fentanyl at any dose in the management of breakthrough pain in cancer subjects on background opioid therapy. The standard of care for these breakthrough pain episodes is a rapid onset, short acting analgesic with minimal associated sleepiness. Oral morphine, oxycodone and hydromorphone are routinely used, but because of slow and variable oral absorption, the pain control is not the best with these products. Oral transmucosal fentanyl citrate OTFC has been used successfully in treating breakthrough pain episodes associated with cancer. OTFC is a lozenge of fentanyl on a stick and is administered by continuously swabbing the interior of the subjects mouth until the product is dissolved approximately 15 to 30 minutes. The buccal route of administration avoids the delay and variability associated with oral absorption. 