Multivitamin [water & fat soluble] + Normal Saline contains folic acid, and folic acid may make the body break down some epilepsy medicines faster. Phenobarbital is one of these, along with phenytoin and primidone. When it is cleared faster, less of it stays in the blood, so it may not control seizures as well. If you take phenobarbital, tell your doctor before using this multivitamin.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.