Topiramate in clinical practice: first year's postlicensing experience in a specialist epilepsy clinic

Topiramate became available for use in October 1995. Meta-analysis of its randomised controlled data suggested that it may be the most potent of the new antiepileptic drugs. The aim of this study was to assess the first year's postlicensing experience in a specialist regional epilepsy clinic.

The case notes of 174 of 178 patients who were prescribed topiramate in the 12 months between November 1995 and October 1996 were retrospectively reviewed. Data were collected on seizure type, classification of epilepsy, presence or absence of learning difficulties, depression, or behavioural problems, co-medication, dosage escalation, efficacy, adverse events, whether or not the patient was still on topiramate and, if not, the reason for withdrawal. Kaplan-Meier survival analysis was used to estimate the overall retention rate and log rank tests were used to determine factors associated with stopping topiramate.

Overall 90 of 174 patients had ceased taking topiramate at the end of the study. The median "survival time" was 427 days (95% CI 362.9-491.1). The cumulative probability for remaining on topiramate at 1 year was 0.549 (95% CI 0.475-0.623). The retention rate in patients in whom topiramate was substituted for another drug was significantly higher than in those in whom it was added to current therapy. Adverse events (CNS related) were the most common reason for stopping topiramate. Eight patients with partial and one patient with juvenile myoclonic epilepsy became seizure free.

There is a significant (20-25%) chance of being intolerant to topiramate at relatively low doses. Substituting topiramate for another antiepileptic drug may reduce the chances of drug withdrawal. If topiramate is tolerated there is a good chance of worthwhile improvement in seizure control. These data, although not derived from randomised controlled trials, represent pragmatic use of novel antiepileptic drugs in "real life" and may be helpful to non-specialists when prescribing topiramate.