The effect of gabapentin on brain gamma-aminobutyric acid in patients with epilepsy

Gabapentin has come into clinical use as adjunctive therapy in the treatment of epilepsy. Designed to mimic gamma-aminobutyric acid (GABA), its mechanism of action remains elusive. In vivo measurements of GABA in human brain were made using H-1 magnetic resonance spectroscopy. We used a 2.1-T magnetic resonance imager-spectrometer and an 8-cm surface coil to measure a 13.5-cm(3) volume in the occipital cortex. GABA levels were measured in 14 patients enrolled in an open-label trial of gabapentin. GABA was elevated in patients taking gabapentin compared with 14 complex partial epilepsy patients, matched for antiepileptic drug treatment. Brain GABA levels appeared to be higher in patients taking high-dose gabapentin (3,300-3,600 mg/day) than in those taking standard doses (1,200-2,400 mg/day). Gabapentin appears to increase human brain GABA levels.