Phensuximide is an anticonvulsant in the succinimide class. For the treatment of epilepsy. Phensuximide suppresses the paroxysmal three cycle per second spike and wave EEG pattern associated with lapses of consciousness in absence (petit mal) seizures. The frequency of attacks is reduced by depression of nerve transmission in the motor cortex. Phensuximide's mechanism of action not understood, but may act in inhibitory neuronal systems that are important in the generation of the three per second rhythm. It's effects may be related to its ability to inhibit depolarization-induced accumulation of cyclic AMP and cyclic GMP in brain tissue.