Sublingual Methadone for the Management of Cancer Breakthrough Pain

Inclusion Criteria: * \> 18 years of age * Experiences episodes of breakthrough pain which respond to opioid therapy * Controlled baseline pain * Cognitive status sufficient for accurate completion of assessment form * Willing to provide written informed consent * Ability to hold a volume of 1 cc of water under the tongue for 5 minutes Exclusion Criteria: * Currently or has received methadone during the previous week * Recent history of substance abuse * Severe respiratory impairment or other contraindications to opioids * Recently received therapies that had the potential to alter pain intensity or response to analgesics * Symptomatic anemia