Naltrexone should correctly be referred to as naltrexone hydrochloride, a medication that allows for the gradual detoxification of patients who have become dependent on opioids. Naltrexone hydrochloride is an opioid receptor antagonist that blocks the pharmacologic effects of exogenous opioids to aid in relapse prevention after detoxification of opioid-dependent individuals. Contraindications to the use of the drug include the application of persons with a history of hypersensitivity to naloxone hydrochloride, persons on opioid analgesics, persons with opioid addiction and unabated, persons who have abruptly discontinued opioids, persons who have a positive urine test for opioids, persons who have failed to be motivated by naloxone hydrochloride, persons with acute hepatitis or hepatic failure or poor hepatic function. Adverse reactions such as gastrointestinal discomfort, nausea, vomiting, poor appetite, fatigue, difficulty sleeping, hepatocellular damage, anxiety, agitation and abdominal pain may occur after administration. Specific medication should be administered under the guidance of a specialist, and should not be used without authorization.