Management of Phenytoin (Dilantin) Toxicity
The management of phenytoin toxicity primarily involves discontinuation of the drug, supportive care, and close monitoring as there is no specific antidote available. 1
Clinical Manifestations of Phenytoin Toxicity
Symptoms correlate with serum levels and typically progress in the following order 1, 2:
Cardiovascular complications such as hypotension and arrhythmias are rare with oral phenytoin toxicity but more common with rapid IV administration 2
Initial Assessment and Management
- Assess airway, breathing, and circulation; provide respiratory support if needed 1
- Monitor vital signs, particularly for hypotension and cardiac arrhythmias 5
- Obtain serum phenytoin level to confirm toxicity and guide management 1, 2
- Immediately discontinue phenytoin administration 1, 6
- Correct electrolyte abnormalities, particularly ensuring serum potassium is greater than 4 mM/L 5
- Ensure adequate oxygenation 5
Supportive Care
- Provide continuous cardiac monitoring for patients with severe toxicity 5
- Implement fall precautions due to ataxia and unsteady gait 3
- Manage nausea and vomiting with antiemetics 2
- Position patient to prevent aspiration if consciousness is impaired 2
- Monitor for and treat seizures if they occur (paradoxical seizures may occur with toxicity) 4
Gastrointestinal Decontamination
- Consider activated charcoal if the patient presents early after ingestion 2
- Multiple-dose activated charcoal may enhance elimination, though clinical benefit remains controversial 7
Enhanced Elimination Methods
- Hemodialysis can be considered in severe cases, though effectiveness is limited since phenytoin is highly protein-bound 1
- There is insufficient evidence supporting the routine use of plasmapheresis or hemoperfusion 2
What NOT to Do
- Do not administer lidocaine or additional phenytoin to treat phenytoin toxicity-induced arrhythmias 5
- Avoid medications that may worsen CNS depression 1
- Avoid drugs that may interfere with phenytoin metabolism or protein binding 2
Monitoring and Follow-up
- Continue monitoring serum phenytoin levels until they return to therapeutic range 6
- Be aware that phenytoin follows zero-order kinetics in overdose, resulting in prolonged elimination and extended duration of symptoms 2
- Symptoms typically resolve completely with supportive care and drug withdrawal 3, 6
Special Considerations
- Patients with hypoalbuminemia, renal failure, or hepatic dysfunction are at higher risk for toxicity at standard doses 4
- Drug interactions (particularly with clarithromycin, erythromycin, and other medications) can precipitate phenytoin toxicity 5, 3
- Neonates have increased risk of toxicity due to decreased protein binding 5