[Possible gabapentin phenytoin interaction].
BACKGROUND
We report a possible case of gabapentin induced phenytoin toxicity.


METHODS
White man, 26 years old, chronically treated with phenytoin (for the past 4 years) and gabapentin (for the past 17 months). He was seen after complaining of dysarthria, ataxia and vertigo for the past 3 months, although having noted slight dizziness and a general, though undefined, indisposition from the start of taking gabapentin. The total and free serum levels of phenytoin found were clearly toxic. Gabapentin was discontinued definitively, and phenytoin for the next 7 days. The clinical symptoms had disappeared completely and phenytoin returned to within therapeutic levels. According to the criteria of causation it can be considered a possible adverse reaction caused by phenytoin related to incorporation of gabapentin. The mechanisms of this possible drug interaction are discussed, with emphasis on cytochrome P450 metabolism.


CONCLUSIONS
The present case is a warning of the possible interaction of a drug (gabapentin) not contemplated when starting or when monitoring an antiepileptic treatment.
Sánchez-Romero
A
A
Servicio de Farmacología Clínica, Complejo Hospitalario Universitario de Albacete, Albacete, 02006, España. asanchez@hgab.insalud.es
Durán-Quintana
J A
JA
García-Delgado
R
R
Margarito-Rangel
C
C
Poveda-Andrés
J L
JL
D000085:Acetates / Q000009:adverse effects*; D000328:Adult; D000588:Amines; D000927:Anticonvulsants / Q000009:adverse effects*; D003509:Cyclohexanecarboxylic Acids; D004347:Drug Interactions; D000077206:Gabapentin; D006801:Humans; D008297:Male; D010672:Phenytoin / Q000009:adverse effects*; D005680:gamma-Aminobutyric Acid
D000085:Acetates; D000588:Amines; D000927:Anticonvulsants; D003509:Cyclohexanecarboxylic Acids; D005680:gamma-Aminobutyric Acid; D010672:Phenytoin; D000077206:Gabapentin