Acute phenytoin toxicity followed by seizure breakthrough from a ticlopidine-phenytoin interaction.
OBJECTIVE
To review a case of a drug-drug interaction between phenytoin sodium and ticlopidine hydrochloride that resulted in acute phenytoin toxicity and permanent memory loss.


METHODS
A 63-year-old man who was maintained with a stable dose of phenytoin for treatment of seizures began treatment with ticlopidine following percutaneous transluminal angioplasty and stent placement. Within 3 weeks of beginning treatment with ticlopidine, he experienced acute clinical toxic effects of phenytoin with a maximum measured phenytoin concentration of 162.4 micromol/L. Phenytoin concentration decreased to 36 micromol/L after discontinuing treatment with ticlopidine and reducing the phenytoin dose. Subsequently, the patient developed probable complex partial status epilepticus.


CONCLUSIONS
Ticlopidine is a metabolic inhibitor of several drugs. Because of the potential for acute and permanent adverse effects from a drug-drug interaction, phenytoin concentrations should be carefully monitored when beginning or ending ticlopidine therapy.
Department of Neurology, University of Cincinnati College of Medicine, Ohio, USA.
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Privitera
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Welty
D004347:Drug Interactions; D017029:Epilepsy, Complex Partial / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010672:Phenytoin / Q000009:adverse effects* / Q000627:therapeutic use; D013988:Ticlopidine / Q000009:adverse effects* / Q000627:therapeutic use; D013997:Time Factors
D010672:Phenytoin; D013988:Ticlopidine