Paradoxical Seizure Response to Phenytoin in an Epileptic Heroin Addict.

BACKGROUND

Phenytoin has a narrow therapeutic window and seizures can occur at both ends of the spectrum.

CASE REPORT: A 41-year-old man with a history of a seizure disorder and heroin addiction presented with dizziness following 2 generalized tonic-clonic seizures that occurred earlier that day. The patient had received a loading dose of phenytoin for seizures associated with a subtherapeutic level 5 days previously. Initial evaluation revealed an elevated phenytoin level of 32.6 mcg/mL and an opiate-positive toxicology screen. Levetiracetam was started on the day of presentation and phenytoin was held until the level returned to the therapeutic range. The patient's dizziness resolved and he had no additional seizures.

CONCLUSIONS

Evaluation for reversible causes of seizure activity along with anticonvulsant administration is generally the standard of care for breakthrough seizures. Phenytoin blood levels, if supratherapeutic, may be at least partially responsible for breakthrough seizure activity; in this circumstance, holding phenytoin and temporarily adding another anticonvulsant may be indicated.