The investigators plan to investigate the efficacy and tolerability of scheduled VPA as compared to placebo with as needed basis (PRN) haloperidol (as a back-up in both arms) for treatment of hyperactive or mixed delirium. Patients will be randomized to scheduled VPA or placebo (normal saline) and both arms will have flexible PRN dosing of haloperidol. Thus, the investigators plan to learn the time to delirium resolution in patients treated with VPA versus placebo; percentage of patients responding to VPA versus placebo; tolerability of VPA versus placebo. If addition of scheduled VPA proves to shorten time to delirium resolution as compared to placebo, lead to less use of haloperidol, and/or have fewer side effects, it would provide a very important addition to our limited evidence-based repertoire of delirium treatment. Moreover, this pilot study would then pave the way for the bigger randomized control trial powered to detect its effect size.