Topiramate (TPM) is a widely-used
drug for the treatment of
epilepsy. It is useful for several types of partial-onset and generalized-onset
seizures, and is therefore considered a broad-spectrum agent. It is also effective as a prophylactic against
migraine headaches. TPM was first approved for prescription use in 1996. In various countries it is now approved for adjunctive and monotherapy of partial-onset
seizures and for
therapy of
generalized tonic-clonic seizures of nonfocal origin, for children and adults. For initial monotherapy of new-onset
seizures, a target dose of 100 mg/day for adults is recommended. Adjunctive use with
enzyme-inducing drugs and use for refractory
seizures requires higher dosages, though the optimum dose for most patients does not exceed 400 mg/day. Excretion is primarily renal and TPM is not a significant hepatic
enzyme inducer. Although it is usually safe and well-tolerated, adverse effects limit use in about 25% of patients. The most salient of these is
cognitive dysfunction, especially problems with expressive speech and verbal memory.
Weight loss, renal stones,
paresthesias and other central nervous system side effects may occur. Tolerability is improved by low initial doses and slow titration to effect.