Modification of cortical excitability induced by gabapentin: a study by transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) was employed before and after a sin gle dose of gabapentin to evaluate how this drug affects the activity of ex citatory and inhibitory circuits within the motor cortex. Eleven healthy vo lunteers were studied. For the evaluation of cortical excitability, the fol lowing parameters were taken into account: resting and active motor thresho ld (RMT, AMT); cortical silent period (CSP); and intracortical. inhibition (ICI) and facilitation (ICF). Peripheral silent period (PSP) was also detec ted. All parameters were measured before and 3 and 24 hours after 800 mg ga bapentin was administered in a single oral dose. Gabapentin deepened the IC I and suppressed the ICF at 3 h but not at 5 h after dosing. We conclude th at, in the normal human brain, gabapentin may act on intracortical excitabi lity by shifting the balance towards less excitation and more inhibition.