title: Effect of levetiracetam on human corticospinal excitability.
abstract: OBJECTIVE
  To investigate whether levetiracetam (LTC) alters corticospinal excitability in humans.
  
  
  BACKGROUND
  Although the antiepileptic activity of LTC is well recognized, its mechanism of action has yet to be determined. Transcranial magnetic stimulation (TMS) has been used to investigate the pharmacologic effects of various antiepileptic drugs on human corticospinal excitability.
  
  
  METHODS
  The authors performed TMS before and after double-blind administration of 3000 mg LTC or placebo in six healthy volunteers. TMS measurements included resting and active motor threshold (MT), recruitment curve of motor-evoked potential amplitudes, intracortical inhibition, and facilitation using the paired-pulse technique and silent period. F-wave and compound muscle action potential (CMAP) were also measured.
  
  
  RESULTS
  In recruitment curve measurements, motor-evoked potential amplitude was reduced for LTC with high stimulation intensity (130% and 140% of resting MT) compared with placebo (p < 0.05 and p < 0.01), but not with relatively low stimulation intensity (110% and 120%). The changes in other TMS measurements as well as F-wave and CMAP after LTC did not differ significantly from those observed after placebo administration.
  
  
  CONCLUSIONS
  These results suggest that LTC reduces the corticospinal neuronal response to magnetic stimulation, preferentially affecting less excitable neurons. The lack of change in F-wave and CMAP suggests that this effect is mainly derived from the motor cortex.
authors.affiliation: Human Motor Control Section ,NINDS, National Institutes of Health, Bethesda, MD 20892-1428, USA.
authors.forename: Y H
authors.initials: YH
authors.lastname: Sohn
authors.forename: A
authors.initials: A
authors.lastname: Kaelin-Lang
authors.forename: H Y
authors.initials: HY
authors.lastname: Jung
authors.forename: M
authors.initials: M
authors.lastname: Hallett
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000494:pharmacology*; D004311:Double-Blind Method; D055590:Electromagnetic Phenomena; D004576:Electromyography / Q000187:drug effects / Q000379:methods; D019054:Evoked Potentials, Motor / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D000077287:Levetiracetam; D008297:Male; D010889:Piracetam / Q000031:analogs & derivatives / Q000494:pharmacology*; D011712:Pyramidal Tracts / Q000187:drug effects* / Q000502:physiology
chemical_list: D000927:Anticonvulsants; D000077287:Levetiracetam; D010889:Piracetam