Side effects of<unk>  at normal therapeutic doses can include: A rare side effect is respiratory depression. Neurotoxicity<unk>  had been thought to cause Olney's lesions when administered intravenously; however, this was later proven inconclusive, due to lack of research on humans. Tests were performed on rats, giving them 50 mg or more every day for as long as a month. Neurotoxic changes, including vacuolation, have been observed in posterior cingulate and retrosplenial cortices of rats administered other NMDA receptor antagonists such as PCP, but not with<unk> . Dependence and withdrawal In many documented cases,<unk>  has produced psychological dependence in people who used it recreationally. It is considered less addictive than the other common weak opiate cough suppressant, codeine. Since<unk>  also acts as a serotonin reuptake inhibitor, users report that regular recreational use over a long period of time can cause withdrawal symptoms similar to those of antidepressant discontinuation syndrome. Additionally, disturbances have been reported in sleep, senses, movement, mood, and thinking.
Dextromethorphan
Nalorphine
Pethidine
Dextrorphan
Aceclidine
Betamethadol
Fentanyl
Procaine