DXM is an opioid derivative, making the risk of overdosing very real, which may present as symptoms such as seizures, tachycardia, hyperexcitability, toxic psychosis, dystonia (involuntary muscle contractions), blurred vision, ataxia, nystagmus, or serotonin syndrome. There have also been cases of closed-eye hallucinations, dissociation, acute episodic psychosis, coma or deaths.