Paradoxical intoxication--a complication of anticonvulsant administration

Area of Science:

• Neurology
• Clinical Pharmacology

Background:

• High anticonvulsant levels can cause toxicity.
• Some patients experience paradoxical effects.

Purpose of the Study:

• Define and describe paradoxical intoxication.
• Identify contributing factors and therapeutic strategies.

Main Methods:

• Literature review of documented cases.
• Analysis of serum drug levels and clinical presentation.

Main Results:

• Paradoxical intoxication involves increased seizures with high hydantoin or carbamazepine levels.
• Serum levels above 40 µg/mL for phenytoin/mephenytoin or 20 µg/mL for carbamazepine are implicated.
• Reduced seizure control correlates with higher drug levels, and improvement with dose reduction.

Conclusions:

• Paradoxical intoxication is a distinct syndrome.
• Patients with impaired self-assessment may be at higher risk.
• Dose reduction of the offending anticonvulsant is the primary treatment.