Addiction to dissociative substances (e.g., phencyclidine, ketamine, dextromethorphan, nitrous oxide) can lead to lasting psychological and medical effects. Pharmacotherapies targeted toward addiction to PCP, ketamine, and dextromethorphan are not well studied. Available pharmacotherapies typically only treat the acute intoxication phase. Some research suggests that naltrexone may be useful in reducing cravings for ketamine and dextromethorphan.