To determine the rate of adverse events during the dosing and maintenance stages of therapy, Doctor Frederick G. Freitag, Associate Director of the Diamond Headache Clinic in Chicago, and colleagues, reviewed four randomized, placebo-controlled trials. All of the subjects in the trials had taken either Topamax 100 mg/day (386 subjects), 200 mg/day (514), or placebo (445). The dose of Topamax was increased by 25 mg weekly increments until the assigned maximum dose was reached. The maximum dose was then maintained for either 12 (213 subjects) or 18 weeks (1367). The number of patients reporting adverse events during either the dosing or maintenance period was assessed.

Results
For all Topamax doses, the incidence of adverse events was consistently higher in the dosing versus the maintenance period. For example, patients receiving Topamax 100 mg/day or placebo, incidence rates for paresthesia were 49% (topamax 100 mg/day) and 4% (placebo) during the dosing phase, compared with 12% (topamax 100 mg/day) and 8% (placebo) during maintenance.

Incidence rates for fatigue were 15% (Topamax 100 mg/day) and 8% (placebo) during dosing compared with 2% (Topamax 100 mg/day) and 4% (placebo) during maintenance.

Dr. Freitag and colleagues conclude that most topamax-associated adverse events are mild-to-moderate in severity and occur during the dosing rather than the maintenance period.

Source:
Freitag F, et al. Incidence of adverse events during the titration and maintenance phases of placebo-controlled trials of topiramate for migraine prevention. Presented at the World Congress of Neurology in Sydney, Australia, November 5-11, 2005.