Primary Outcome Measures:
- Individual (each patient) and mean (each treatment) topiramate plasma concentration-time profiles.
Secondary Outcome Measures:
- Incidence of adverse events throughout the study. Changes from pretreatment to the end of posttreatment phase in take-home records, clinical laboratory results, physical & neurologic examination results, ECGs, renal ultrasounds, vital sign measurements
This is a open-label, randomized (patients are assigned different treatments based on chance), dose comparison, multicenter study of topiramate in infants of age 1-24 months with refractory partial-onset seizures (POS). The trial will evaluate the pharmacokinetics, safety, and tolerability of topiramate used as additional treatment in infants with refractory POS. Topiramate is administered as liquid and sprinkles as adjunct (additional treatment) to concurrent anticonvulsant therapy. The study will consist of 4 phases: a pretreatment phase that includes screening (up to 7 days) and baseline (1 day), an open-label treatment phase (up to 6 weeks), an open-label extension phase (54 weeks), and a posttreatment phase (up to 4 weeks). Seizure diaries will be maintained throughout the study by the patients' parents, legally acceptable representatives, or caregivers. In the open-label treatment phase, patients will be randomly assigned to 1 of 4 treatments: topiramate 3, 5, 15, or 25 mg/kg per day. Venous blood samples (four 1 milliliter [mL] samples) will be collected on 2 days during the study to determine plasma concentration of topiramate. Safety will be evaluated throughout the study by monitoring adverse events and by results from clinical laboratory tests (serum chemistry, venous ammonia, hematology, and urinalysis), electrocardiograms (ECGs), vital sign measurements (pulse and blood pressure), physical examination, neurologic examination, Vineland Scales of Adaptive Behavior, renal ultrasound, assessments for adequate food and liquid intake, hyperthermia, oligohydrosis, and rash, and take-home records. Liquid or sprinkles form of topiramate, 3,5,15,or 25mg/kg per day for 54 weeks.