Fentanyl Sublingual Spray in Treating Opioid-tolerant Cancer Patients With or Without Oral Mucositis

DISEASE CHARACTERISTICS: * Diagnosis of cancer and meets 1 of the following criteria: * Mild mucositis, defined as grade 1 (erythema of the mucosa) or 2 (patchy ulcerations or pseudomembranes) on the day of study drug administration. * No mucositis, defined as normal oral cavity upon examination on the day of study drug administration. * Opioid-tolerant, defined as patients who are taking ≥ 60 mg of oral morphine/day, ≥ 30 mg of oxycodone/day, ≥ 8 mg of oral hydromorphone/day, or an equianalgesic dose of another opioid for ≥ 7 days for cancer-related pain. * Persistent pain related to cancer or its treatment over the past 7 days. * No brain metastases with signs or symptoms of increased intracranial pressure. PATIENT CHARACTERISTICS: * Negative pregnancy test. * Agree to be confined to study site for approximately 12 hours, to eat only the food served by the study unit during the study confinement period, and to consume all food provided at the designated meal or snack times. * No history of major organ system impairment or disease that, in the investigator's or his/her designee's opinion, could increase the risk associated with the use of opioids. * No uncontrolled hypertension despite antihypertensive therapy or history of hypertensive crisis within the past 2 years. * No recent history (within the past 2 years) of transient ischemic attacks, neural vascular disease, stroke, or cerebral aneurysms. * No intolerable side effects to opioids or fentanyl. PRIOR CONCURRENT THERAPY: * See Disease Characteristics. * More than 30 days since prior investigational agents. * More than 14 days since prior monoamine oxidase inhibitors. * No prior participation in either Insys Fentanyl Sublingual Spray Phase III study INSYS-INS-05-001 or INSYS-INS-06-007. * No other concurrent use of any fentanyl product. * Patients who have received Actiq®, Fentora®, or Duragesic® are eligible after a 7-day washout. * No concurrent medications (prescription, over-the-counter, vitamin, or herbal substances) except for hormonal contraceptives and/or ≤ 3 doses of acetaminophen at ≤ 1 g each.