ZARS Pharma is developing a Matrix Transdermal Fentanyl/CHADD (Controlled Heat-Assisted Drug Delivery) Drug Delivery System to be used for the treatment of chronic and breakthrough pain. The Matrix Transdermal Fentanyl/CHADD Drug Delivery System has been designed to provide long-term delivery of fentanyl for the treatment of chronic pain as well as intermittent increases in fentanyl concentrations for the treatment of breakthrough pain. Breakthrough pain is defined as a transitory exacerbation of pain that occurs on a background of otherwise stable pain in a patient receiving chronic opioid therapy.