Opioid antagonists are medications that block the effects of opioids, which are substances that can relieve pain but also have a high potential for addiction. These antagonists work by binding to the same receptors in the brain that opioids target, preventing the opioids from producing their effects. Common examples include naloxone and naltrexone. These medications are often used in emergency situations to reverse opioid overdoses, restoring normal breathing and consciousness. They can also be part of treatment plans for individuals recovering from opioid use disorder, helping to reduce cravings and prevent relapse by blocking the euphoric effects of opioids.