The investigators believe the fentanyl transdermal patch currently available has several limitations including the requirement of a long time to reach peak effect and that it cannot be used to treat breakthrough pain (short-lasting episodes of increased pain). ZARs' preliminary data, using its patented controlled, heat-aided drug delivery (CHADD) technology has demonstrated an ability to significantly enhance the dermal absorption of fentanyl from commercially available fentanyl skin patches. The aim of the proposed research is to develop a CHADD system that can significantly shorten the time it takes a fentanyl skin patch to reach peak effect and to prove the concept that CHADD can be utilized to produce a rapid bolus of fentanyl from skin patches, sufficient to treat breakthrough pain. PROPOSED COMMERCIAL APPLICATION: The commercial product will be prescribed by doctors for the treatment of both chronic pain (including severe cancer-related pain) and breakthrough pain (short-lasting episodes of increased pain).