Effects of gabapentin on brain GABA, homocarnosine, and pyrrolidinone in epilepsy patients.
OBJECTIVE
Gabapentin (GBP) was introduced as an antiepileptic drug (AED) and has been used in the management of neuropathic pain. We reported that daily dosing increased brain gamma-aminobutyric acid (GABA) in patients with epilepsy. This study was designed to determine how rapidly brain GABA and the GABA metabolites, homocarnosine and pyrrolidinone, increase in response to the first dose of GBP.


METHODS
In vivo measurements of GABA, homocarnosine, and pyrrolidinone were made of a 14-cc volume in the occipital cortex by using a 1H spectroscopy with a 2.1-Tesla magnetic resonance spectrometer and an 8-cm surface coil. Six patients (four women) were studied serially after the first oral dose (1,200 mg) of GBP. Five patients (three women) taking a standard daily dose (range, 1,200-2,000 mg) of GBP were rechallenged with a single high dose (2,400 mg).


RESULTS
The first dose of GBP increased median brain GABA by 1.3 mM (range, 0.4-1.8 mM) within 1 h. Homocarnosine and pyrrolidinone did not change significantly by 5 h. Daily GBP therapy increased GABA (0.5 mM; 95% CI, 0.2-0.9), homocarnosine (0.3 mM; 95% CI, 0.2-0.4), and pyrrolidinone (0.10 mM; 95% CI, 0.06-0.14). Rechallenging patients taking GBP daily increased median brain GABA by 0.4 mM (range, 0.3-0.5) within 1 h.


CONCLUSIONS
GBP promptly elevates brain GABA and presumably offers partial protection against further seizures within hours of the first oral dose. Patients may expect to experience the anticonvulsant effects of increased homocarnosine and pyrrolidinone with daily therapy.
Petroff
O A
OA
Department of Neurology, Yale University, New Haven, Connecticut, USA.
Hyder
F
F
Rothman
D L
DL
Mattson
R H
RH
D000085:Acetates / Q000494:pharmacology* / Q000627:therapeutic use; D000328:Adult; D000588:Amines; D000927:Anticonvulsants / Q000494:pharmacology* / Q000627:therapeutic use; D001923:Brain Chemistry / Q000187:drug effects; D002336:Carnosine / Q000031:analogs & derivatives* / Q000032:analysis; D003509:Cyclohexanecarboxylic Acids; D004305:Dose-Response Relationship, Drug; D004827:Epilepsy / Q000188:drug therapy / Q000378:metabolism*; D005260:Female; D000077206:Gabapentin; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000737:chemistry* / Q000187:drug effects*; D011760:Pyrrolidinones / Q000032:analysis*; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D000085:Acetates; D000588:Amines; D000927:Anticonvulsants; D003509:Cyclohexanecarboxylic Acids; D011760:Pyrrolidinones; C005038:homocarnosine; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D002336:Carnosine