Switchability Study Between Brand and Generic Topiramate

A Clinical Pharmacokinetics Comparing Brand and Generic Topiramate in Epilepsy Patients : A Open-label,Randomised, Three-period Crossover Study

Generic antiepileptic drugs (AED) achieve blood concentration similar to the brand AED. However, controversies exist about efficacy and safety of substituting generic AEDs. Because even minor absorption and kinetic differences can elicit a breakthrough seizure in patients who are changed to a generic AED from brand AED. Therefore, more ideal evaluation of interchangeability from the brand AEDs to generic formulation of the same drug is three-way or four-way crossover study, which can evaluate within-subject variability in pharmacokinetic and pharmacodynamic. Investigator designed four-way crossover study aimed to assess bioequivalence of brand and generic topiramate, to measure trough serum level , and to evaluate efficacy, tolerability and side effect of generic topiramate.

For pharmacokinetics, blood samples was taken after receiving Topamax 100mg twice a day in first visit day. For pharmacokinetics, blood samples was taken after receiving Topamed 100mg twice a day in second visit day. For pharmacokinetics, blood samples was taken after receiving Topamax 100mg twice a day in third visit day. For pharmacokinetics, blood samples was taken after receiving Topamed 100mg twice a day in third visit day.

For pharmacokinetics, blood samples was taken after receiving Topamed 100mg twice a day in first visit day. For pharmacokinetics, blood samples was taken after receiving Topamax 100mg twice a day in second visit day. For pharmacokinetics, blood samples was taken after receiving Topamed 100mg twice a day in third visit day. For pharmacokinetics, blood samples was taken after receiving Topamax 100mg twice a day in third visit day.

To Measure the Area under the plasma concentration versus time curve, serum trough drug level of generic and brand topiramate through pharmacokinetics study.

All comparisons of the drug formulations fulfill the bioequivalence criteria, with all 90% Confidential intervals(CIs) for Cmax, AUC, and Ctrough being within the 80-125% acceptance range. Scaling average bioequivalence that the acceptable bioequivalence limits of 90% CI of generic to brand topiramate will be those limits that are within and/or similar to the bioequivalence limits of the 90% CI of Brand to Brand topiramate

[ Time Frame: 0.5, 1, 1.5, 2, 3, 4, 6, 8, and 12 hours after taking the brand or generic topiramate during 7 days]

Number of Participants with Adverse Events as a Measure of Safety and Tolerability of generic topiramate in subjects with epilepsy

Inclusion Criteria: aged 18-65 years Patients with epilepsy who take by topamax 100mg bid or who need to take topamax 100mg bid Exclusion Criteria: poor compliance subjects whose dose of antiepileptic drug are changed during the study subjects whose seizure is not well-controlled judged by neurologist history of any kind of drug allergy pregnancy or nursing existing or recent significant disease (cardiac, hepatic, or renal disease, severe diabetes mellitus, sepsis, etc.)

Bialer M, Midha KK. Generic products of antiepileptic drugs: a perspective on bioequivalence and interchangeability. Epilepsia. 2010 Jun;51(6):941-50. doi: 10.1111/j.1528-1167.2010.02573.x. Epub 2010 Apr 8.

Erickson SC, Le L, Ramsey SD, Solow BK, Zakharyan A, Stockl KM, Harada AS, Curtis B. Clinical and pharmacy utilization outcomes with brand to generic antiepileptic switches in patients with epilepsy. Epilepsia. 2011 Jul;52(7):1365-71. doi: 10.1111/j.1528-1167.2011.03130.x. Epub 2011 Jun 21.