Topiramate (RWJ 17021) is a unique antiseizure medication that is used in the treatment of partial and generalized seizures. Topiramate has been rarely associated with hepatic injury and largely when used in combination with other anticonvulsant medications.

Intraperitoneal injection of 20 and 40 mg/kg topiramate demonstrated a dose-dependent inhibition of both tonic convulsions and absence seizures. Intraperitoneal administration of topiramate at doses ranging from 25-100 mg/kg dose-dependently increased the threshold for pentylenetetrazol (PTZ)-induced clonic seizures. Topiramate was dose-effectively potent in suppressing acute seizures induced by perinatal hypoxia, with an ED50 of 2.1 mg/kg. Additionally, in DBA/2 mice, topiramate inhibited audiogenic seizures, confirming its anticonvulsant efficacy.

In whole-cell voltage-clamp recordings from principal neurons of the basolateral nucleus of the rat amygdala, low concentrations of Topiramate selectively inhibit excitatory postsynaptic currents (EPSCs) mediated by pharmacologically isolated kainate receptors that contain the GluR5 subunit. Topiramate also noticeably reduces AMPA receptor-mediated EPSCs, albeit with less potency. Additionally, Topiramate slightly inhibits the sustained component of Na+ currents in isolated neurons, and after blocking Ca2+ and K+ currents, diminishes the peak of Na+-dependent persistent action potentials induced in layer V pyramidal neurons. The compound selectively inhibits synaptic responses mediated by the GluR5 kainate receptor. Moreover, Topiramate impedes the action of voltage-sensitive Na+ channels and non-N-methyl-D-aspartate receptors, while potentiating inhibition mediated by gamma-aminobutyric acid (GABA).