Chronic pain, often defined as pain lasting longer than 3 months or past the time of normal tissue healing, is extremely common. According to a recent Institute of Medicine report, up to one-third of U.S. adults report chronic pain. Chronic pain is a major cause of decreased quality of life and disability and is often refractory to treatment. There has been a dramatic increase over the past 10 to 20 years in the prescription of opioid medications...