The objective of our study was to investigate the effect of topiramate (TPM) on the Lyapunov exponent of EEG by means of quantitative pharmacoelectroencephalography (QPEEG) and nonlinear analysis methods. One dose of TPM was administrated to epileptics and healthy adults. EEG samples were obtained prior to and at regular intervals (at 0.5, 1, 2, 4, 6, 8, 12, 24 hours) within the 24 hours following the administration of TPM. EEG activity was processed with nonlinear analysis methods. The Lyapunov exponent of the scalp areas was calculated through 60 s epochs without artifacts after each recording. The statistical difference between baseline predrug assessment and each postdrug control was calculated by computing the paired t test. Results showed that the Lyapunov exponent increased first, then decreased, then increased finally. We conclude that TPM can change the complexity of EEG.