My Husband Has Glioblastoma, Is Taking 500 Mg Keppra Twice

My husband has glioblastoma, is taking 500 mg Keppra twice a day, dexametnasone 4 mg twice a day and Lorazepam as needed. He is very restless at night, not sleeping much. Hospice doctor prescribed trazodone, and then when that didn't seem to work, haloperidol, which also didn't seem to help. We've also tried diphenhydromine, which didn't do much. Now they're prescribing valproic acid 250 mg twice a day. What exactly is this used for? And if I start him on this, will he have to continue taking it to prevent seizures, like the Keppra?