Opioid medications are frequently used for the treatment of moderate to severe pain; however, individuals who use opioids have a high risk of becoming addicted. Opioid users who abruptly stop using opioid drugs may experience withdrawal symptoms, including drug craving, sweating, sleep disruption, nausea, irritability, and pain. Hyperalgesia, a severe and excessive sensitivity to pain, is a serious condition that may also occur when opioid use is reduced or discontinued. Opioid medications affect both the pain inhibitory and facilitatory systems, meaning that while they are effective at treating pain in many individuals, they also have the ability to intensify pain and cause hyperalgesia in some opioid users. Three medications, dextromethorphan, gabapentin, and oxycodone, may alleviate the symptoms of hyperalgesia and lessen an individual's sensitivity to pain. Further research is needed to confirm the benefits of these medications for opioid addicts. The purpose of this study is to compare the effectiveness of dextromethorphan, gabapentin, and oxycodone at reducing opioid-induced hyperalgesia in methadone-maintained opioid addicts.