Mysoline (MY-so-leen) is used to treat partial seizures with or without secondary generalization and generalized tonic clonic (grand mal) seizures. It is available in liquid and tablets. Mysoline is metabolized (processed by the body) into phenobarbital and phenoethylmelanamide, both of which have antiepileptic effects. Like phenobarbital, Mysoline is not effective against absence or myoclonic seizures. Side effects include drowsiness, difficulty thinking, nausea, mental changes and unsteadiness. It is primarily used as an add-on drug. Again, like phenobarbital, if Mysoline is to be discontinued, it has to tapered slowly to avoid rebound seizures or other negative effects. Safety in pregnancy has not been established. Women who are taking this medication and who wish to become pregnant should discuss treatment options with their physicians before the pregnancy begins.