Vimpat is brand new to broad market, though tested for years as a previous poster noted. UCB has keppra going generic, so to continue profits, is marketing keppra xr and vimpat. Vimpat is a newer AED with sodium channel effect with a proposed novel mechanism. As adunctive, and possibly later on, monotherapy it looks promising. It has not been used enough to have people publishing the "common side effect" profile like other meds already have. As a newer and "precise" seizure med hopefully it's side effect profile will be low.