Opioids refer to a class of analgesics or painkillers derived from the poppy plant. They work by binding to the specific receptors in the brain in order to alter pain signals. Opioids are widely used to control pain with a severe intensity that fails to respond to common analgesic medication. They are only available for medicinal use and can be purchased with a valid prescription. Some common examples of opioids include morphine, methadone, oxycodone, hydrocodone, etc.