Kapvay is a prescription drug used in treating high blood pressure, cancer pain and attention deficit hyperactivity disorder (ADHD). Kapvay belongs to the centrally acting alpha-agonist hypotensive agents group of drugs. The drug functions by decreasing heart rate and relaxing blood vessels. The drug also prevents pain signals from being sent to the brain. This drug comes in patch, extended-release tablet, and tablet forms. It also comes in an injectable form that can be given by a medical professional.