Is The Drowsy Feeling And Sedation More Likely From Depakote Or Zyprexa When I Am Bipolar And Taking Lamotrigine As Well?

My husband is bipolar 1 and is on 1500 mg of Depakote ER and 5 mg of zyprexa at night and 1.5 mg zyprexa and 25 mg of lamotrigine in am. We just reduced the Depakote by 500 mg last night but he’s still having somnolence. Is the Depakote still too high? Or is the zyprexa making him too drowsy?