Long-term Safety Study of Sublingual Fentanyl Tablets in Cancer Patients

Inclusion Criteria: * Males or females 17 years of age or older. * Stable cancer-related pain. * Are receiving a stable, fixed-schedule oral opioid regimen equivalent to 60 to 1000 mg of oral morphine per day or transdermal fentanyl therapy equivalent to 50 to 300 µg/h, and are on a stable dose of opioid medication for relief of breakthrough pain. * Experiencing 1-4 episodes of breakthrough pain per day. * Meet the criteria defined in the Eastern Cooperative Oncology Group (ECOG) Performance Status for Grade 0, 1, or 2. Exclusion Criteria: * Have previously been exposed to EN3267. * Are pregnant or lactating. * Have uncontrolled or rapidly escalating pain. * Have any clinically significant condition that would, in the investigator's opinion, preclude participation in the study or compromise data collection. These conditions may include cardiopulmonary disease, and/or neurologic/psychologic conditions. * Are scheduled to take MAOIs (monoamine oxidase inhibitors) during the study. * Are scheduled to receive anti-neoplastic therapy that, in the investigator's opinion, will influence assessment of breakthrough pain. * Are scheduled to receive an investigational drug other than EN3267 during the course of the study. * Have hypersensitivity, allergy or contraindication to fentanyl. * Have significant prior history of substance abuse or alcohol abuse. * Would have difficulty complying with the protocol, as assessed by the investigator. * Are unable to read, write, or comprehend the English language in order to complete diaries.