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Phenytoin encephalopathy as probable idiosyncratic reaction: case report
Epilepsia
|September 1, 1977
Summary
Phenytoin (DPH) encephalopathy can occur even with low plasma levels, presenting as increased seizures and mental changes. Physicians should consider discontinuing DPH if these symptoms arise, regardless of blood concentration.
Area of Science:
- Neurology
- Pharmacology
Background:
- Phenytoin (DPH) is a common antiepileptic drug.
- Encephalopathy is a serious neurological complication.
Observation:
- A patient developed phenytoin encephalopathy despite a low plasma DPH concentration (2.8 microgramg/ml) on an adequate oral dosage (5 mg/kg/daily).
- The patient experienced increased seizures, altered EEG, and mental status changes.
- The reaction was deemed idiosyncratic, not toxic or allergic, supported by normal free DPH levels, a delayed morbilliform rash, normal protidogram, and negative intradermal DPH test.
Findings:
- Low plasma phenytoin levels do not exclude the possibility of DPH-induced encephalopathy.
- Idiosyncratic reactions to DPH can manifest as severe neurological symptoms.
Implications:
- Clinicians should maintain a high index of suspicion for DPH encephalopathy in patients with epilepsy, even with low serum DPH levels.
- Unexpected neurological deterioration during DPH therapy warrants prompt evaluation and potential discontinuation of the drug.
- This case highlights the complexity of DPH pharmacokinetics and pharmacodynamics in certain patient populations.