Multiple complications and withdrawal syndrome associated with quetiapine/venlafaxine intoxication

Objective: To report a case of quetiapine/venlafaxine intoxication associated with multiple complications and to review their possible relationship with these 2 drugs. Case Summary: A 53-year-old white man was admitted to the hospital for loss of consciousness secondary to voluntary intoxication with venlafaxine and quetiapine. Several complications were attributable to this intoxication including seizures, prolonged coma, respiratory depression, neuroleptic malignant syndrome, prolonged QRS and QTc intervals, and a possible venlafaxine withdrawal syndrome. Discussion: Quetiapine could be responsible for the neuroleptic malignant syndrome presented in this case. Moreover, venlafaxine intoxication, fever, autonomic instability, and myoclonus presented serotonin syndrome as a differential diagnosis. Potential causes of seizures and prolongation of the QRS and QTc intervals are reviewed. Finally, prolonged coma and late venlafaxine withdrawal are discussed with regard to the pharmacodynamics and pharmacokinetics of drug elimination in the context of intoxication. Conclusions: Clinicians should be aware of possible complications following intoxication with atypical antipsychotics and antidepressants, including protracted altered mental status.