An open-label, single arm, observation study, to assess the efficacy and safety of proportional doses of Painkyl® in patients with breakthrough cancer pain.

Inclusion Criteria:

1. cancer patients regularly experienced 1 to 3 breakthrough pain episodes per day that required additional opioids from pain control;
2. a current regimen of opioids equivalent to 60-360 mg/day of oral morphine or 25-150 mcg/hr of transdermal fentanyl for one week or longer;
3. at least partial relief of breakthrough pain by use of opioid therapy;
4. able to self-administer the study medication correctly or has an available adult caregiver to administer the study medication correctly;
5. willing and able to complete patient diary with each pain episode.
6. 20 to 80 years of age;

Exclusion Criteria:

1. rapidly escalating pain (e.g., regularly more than 3 breakthrough pain episodes per day) that are hard to be controlled by analgesics;
2. history of hypersensitivity or intolerance to fentanyl;
3. cardiopulmonary disease that, in the opinion of the investigator, would significantly increase the risk of respiratory depression;
4. psychiatric/cognitive or neurological impairment that would limit the subject's ability to understand or complete the diary;
5. Severe (Grade 4) mucositis (subjects with less than severe mucositis are permitted and must be instructed to not apply the Painkyl® film at a site of inflammation);
6. abnormal oral mucosa which will impede drug absorption;
7. recent history or current evidence of alcohol or other drug substance (licit or illicit) abuse;
8. use of an investigational drug or other rapid-onset opioids drugs within 4 weeks preceding this study;
9. pregnant women or nursing mothers, or positive pregnancy test for women of childbearing potential.

Adult cancer patients experienced breakthrough pain even under around-the-clock narcotic drug treatment.