 Eligible participants were all adults aged 18 or over suffering from Background pain cancer pain whose cancer pain was treated with strong opioids and who had breakthrough pain which met the criteria described by Portenoy.5 stable analgesia in the previous 48 h, controlled background pain in the previous 24 h, transient exacerbation of pain in the previous 24 h. The term strong opioid refers to medicines classified as being on step three of the World Health Organization WHO analgesic ladder. In Egypt the strong opioids available include fentanyl, morphine and hydromorphone. 