epilepsy
"After EEG showed seizure activity, Neurologist started me on 500mg/day Keppra.  At the 4 hr mark, I felt very spaced out. Couldn't think, hazy, slurring speech, lethargic, etc. Neuro suggested I start taking at night, so that I could "sleep through" the odd feeling.  Now, I WAKE up at the 4 hr mark... on the dot, every single night. I still feel spaced out, and find it hard to get comfortable and fall back asleep. Takes me about an hour to fall back asleep. Sleep disturbances cause me to feel tired during day."