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Paradoxical seizures in phenytoin toxicity
H C Chua1, N Venketasubramanian, C B Tan
1Department of Neurology, Tan Tock Seng Hospital, Singapore.
Singapore Medical Journal
|September 16, 1999
Summary
Phenytoin toxicity can cause paradoxical seizures, a rare condition where seizures worsen as phenytoin levels rise. This study highlights three cases, emphasizing the need to consider this adverse effect when managing patients on phenytoin therapy.
Area of Science:
- Neurology
- Clinical Pharmacology
Background:
- Phenytoin is an anticonvulsant medication used to treat epilepsy.
- Phenytoin toxicity is an uncommon but serious adverse effect.
- Predisposing factors for phenytoin toxicity include hypoalbuminemia, chronic renal failure, hepatic dysfunction, and drug interactions.
Observation:
- Paradoxical seizures are a less recognized manifestation of phenytoin toxicity.
- This phenomenon involves seizures worsening as serum phenytoin levels increase.
- Other common signs of phenytoin toxicity include confusion and ataxia.
Findings:
- Three patients presented with paradoxical seizures, a rare adverse effect of phenytoin.
- Serum phenytoin levels in these patients ranged from 38.3 to 46.5 mcg/mL.
- Seizure control was achieved by discontinuing phenytoin and lowering drug levels.
Implications:
- Clinicians should consider paradoxical seizures in patients experiencing worsening seizure control despite therapeutic drug levels.
- Monitoring serum phenytoin levels is crucial for identifying and managing toxicity.
- Understanding this rare adverse effect aids in optimizing patient care and preventing treatment failure.