- known severe allergic reactions to valproate or quetiapine - history of hepatic encephalopathy or end-stage liver disease (childs-pugh class b or worse) - alcohol, or history of alcohol/substance dependence prior to admission - hx of dementia - treatment with an antipsychotic agent in the 30 days before icu admission - baseline qt duration corrected (qtc) interval ≥ 500 msecs - pregnancy - suspected active bacterial, fungal, viral, or other infection (besides covid-19) - in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 3 x upper limit of normal (uln) detected within 24 hours at screening or at baseline - absolute neutrophil count (anc) < 1000/microliter (ul) at screening and baseline - platelet count < 50,000/ul at screening and baseline - individuals < 18 (infants, children, teenagers) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgement, precludes the patient's safe participation in and completion of the study, e.g. active seizure disorder already receiving treatment with lamotrigine - informed consent could not be obtained from the legally authorized representative.

- known severe allergic reactions to valproate or quetiapine - history of hepatic encephalopathy or end-stage liver disease (childs-pugh class b or worse) - alcohol, or history of alcohol/substance dependence prior to admission - hx of dementia - treatment with an antipsychotic agent in the 30 days before icu admission - baseline qt duration corrected (qtc) interval ≥ 500 msecs - pregnancy - suspected active bacterial, fungal, viral, or other infection (besides covid-19) - in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 3 x upper limit of normal (uln) detected within 24 hours at screening or at baseline - absolute neutrophil count (anc) < 1000/microliter (ul) at screening and baseline - platelet count < 50,000/ul at screening and baseline - individuals < 18 (infants, children, teenagers) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgement, precludes the patient's safe participation in and completion of the study, e.g. active seizure disorder already receiving treatment with lamotrigine - informed consent could not be obtained from the legally authorized representative.