What Happens When You Stop Taking Dilantin (Phenytoin)
Stopping Dilantin (phenytoin) suddenly can cause serious problems including seizures that will not stop (status epilepticus), which is why it should always be discontinued gradually under medical supervision. 1
Withdrawal Effects
When discontinuing Dilantin, patients may experience:
- Seizure recurrence or worsening: The primary risk of stopping phenytoin is the return of seizures, which typically occurs due to loss of the therapeutic effect rather than a true withdrawal phenomenon 2
- Timing of seizure risk: Seizures may occur even after the drug has been completely eliminated from the body, with studies showing increased seizure frequency beginning approximately 10 days after phenytoin levels become undetectable 2
- Risk of status epilepticus: Abrupt discontinuation can lead to status epilepticus, a medical emergency characterized by prolonged seizures 1
Safe Discontinuation Process
To minimize risks when stopping Dilantin:
- Gradual tapering: The medication should be tapered slowly rather than stopped abruptly
- Cross-tapering: If switching to another anticonvulsant, the new medication should be started and brought to therapeutic levels before completely discontinuing phenytoin 3
- Medical supervision: Regular monitoring during the tapering process is essential
Post-Discontinuation Effects
After stopping Dilantin, patients may experience:
Resolution of side effects: Many adverse effects of phenytoin will gradually improve, including:
- Gingival hyperplasia (gum overgrowth)
- Hirsutism (excessive hair growth)
- Coarsening of facial features
- Cognitive impairment 4
Improved cognitive function: Phenytoin encephalopathy, which manifests as cognitive impairment and cerebellar syndrome, may resolve after discontinuation 4
Normalization of drug interactions: Phenytoin affects many medications through enzyme induction, and these interactions will gradually resolve after discontinuation 3
Special Considerations
Patients with intellectual disability: These individuals may experience particular improvement in cognitive function and balance after phenytoin discontinuation 4
Monitoring needs: After discontinuation, patients should be monitored for:
- Seizure recurrence
- Changes in effectiveness of other medications previously affected by phenytoin's enzyme-inducing properties
- Improvement in side effects
Important Precautions
Never stop Dilantin without medical supervision: The FDA specifically warns against stopping Dilantin suddenly without first talking to a healthcare provider 1
Alternative medication preparation: If Dilantin is being discontinued due to side effects but seizure control is still needed, alternative anticonvulsants should be established at therapeutic levels before complete withdrawal 3
Monitoring period: Patients should be closely observed during and after the tapering process, with particular vigilance during the period when phenytoin levels become undetectable and for several weeks thereafter 2