seizures
"This artical says it's not known what happens with overdose of Prometrium but I can tell you do not take 2 doses at once. I normally take 800mg/day for last 1/2 of my cycle to suppress catamenial seizures. It works great with no negative side effects. I take 200mg every 6 hours. I recently missed a 200mg dose so I took 400mg at once. I was completely anesthesized for a couple of hours. Body went jelly-like. Everything slowed way down to the point that words came too slowly, if at all. Family opted to take me to the ER. Later was determined I was likely not in danger of dying but was clearly knocked out for a while. Memory of much of those 2 hours is totally lost to me. Family says I was pleasant and cooperative but out of it."