Topiramate, a sulfamate-substituted monosaccharide, is one of the newer anticonvulsants available.
Topiramate is absorbed rapidly and is partially metabolized in the liver and excreted mostly unchanged in urine.
Topiramate is believed to act by blocking voltage-dependent sodi-um channels, enhancing activity of the GABA receptors, and an-tagonizing glutamate receptors.
Topiramate is approved as adjunctive therapy for partial and pri-mary generalized tonic-clonic seizures in adults and children older than age 2 and for children with Lennox-Gastaut syndrome. It may also prove beneficial for other types of seizures and as monother-apy.
· Carbamazepine, phenytoin, and valproic acid may cause de-creased topiramate levels.
· Topiramate may decrease the effectiveness of hormonal contra-ceptives and decrease valproic acid levels.
· CNS depressants may cause additive CNS effect when com-bined with topiramate.
· For renally impaired patients (creatinine clearance less than 70 ml/minute), the topiramate dosage should be reduced by 50%. (See Adverse reactions to topiramate.)