Background: As reported previously, 140 methamphetamine-dependent participants at eight medical
centers in the U.S. were assigned randomly to receive topiramate (N = 69) or placebo (N = 71) in a 13-
week clinical trial. The study found that topiramate did not appear to reduce methamphetamine use
significantly for the primary outcome (i.e., weekly abstinence from methamphetamine in weeks 6–12).
Given that the treatment responses varied considerably among subjects, the objective of this study was
to identify the heterogeneous treatment effect of topiramate and determine whether topiramate could
reduce methamphetamine use effectively in a subgroup of subjects.