I take a low dose of Lexapro in the morning for this and it keeps me fairly level and able to work. I take a very small dose of Trazodone at bedtime as well (25 mg.)

Those along with 100-200mg of Nuvigil keep me going and keep my mood pretty stable, in spite of the MS. My MS neuro told me years ago that the damage done by MS is very commonly bringing on depression symptoms for patients with MS.