Stahl's Essential Psychopharmacology Online
In Collaboration With
Phenytoin
Therapeutics
Brands
• Dilantin, Phenytek, Epanutin
Generic?
Yes
Class
• Antiepileptic drug (AED)
Commonly Prescribed for
(FDA approved in bold)
• Generalized tonic-clonic and complex partial seizures (monotherapy or adjunctive in adults and children)
• Treatment of seizures during or following neurosurgery
• Status epilepticus
• Trigeminal neuralgia
• Glossopharyngeal neuralgia
• Migraine prophylaxis
• Neuropathic pain
• Junctional epidermolysis bullosa
• Preeclampsia (alternative to magnesium sulfate)
• Cardiac arrhythmias (especially glycoside-induced)
• Myotonia
How the Drug Works
• Reduces hyperexcitability, likely by effect on sodium channels
• May modulate T-type calcium channels, but not in the thalamus (unlike AEDs used for absence seizures)
How Long Until It Works
• Seizures - may decrease by 2-3 weeks
• Trigeminal neuralgia - may start working in hours to weeks
If It Works
• Seizures - goal is the remission of seizures. Continue as long as effective and well-tolerated. Consider tapering and slowly
stopping after 2 years without seizures, depending on the type of epilepsy
• Pain - goal is the reduction of pain severity and frequency. If trigeminal neuralgia remits on medication, periodically attempt
to lower dose or discontinue
If It Doesn't Work
• Increase to highest tolerated dose
• Epilepsy: consider changing to another agent, adding a second agent or referral for epilepsy surgery evaluation. Check drug
level
• Pain - try an alternative agent
Best Augmenting Combos for Partial Response or Treatment-Resistance
• Epilepsy: keep in mind drug interactions and their effect on levels
Tests
• During intravenous administration, continuous heart monitoring is required, with frequent blood pressure checks
• Obtain blood counts monthly for the first few months due to risk of blood dyscrasias