Seizures
"I was on Dilantin (300 mg per day) over 20 years of my Air Force career with no side effects and no seizures. I was unknowingly switched to a  generic brand and immediately began having seizures. Attempts to use compensate with Trileptal, Keppra, Vimpat, etc. did not completely remove my seizures like Dilantin. My neurologist is transiting me back to brand name Dilantin so my insurance will cover the cost."