Painkillers such as oxycodone, hydrocodone, morphine and methadone can be prescribed by doctors to treat moderate to severe pain. Brand names of these drugs include OxyContin®, Percocet®, Vicodin®, Percodan®, Tylox®, and Demerol®. Fentanyl is a synthetic opioid pain reliever and is many times more powerful than other opioids. Heroin is an illegal opioid. All these opioids can have serious risks and side effects according to the Centers for Disease Control and Prevention.