Phenytoin is Not a Mental Health Medication

Phenytoin is an antiepileptic drug used to treat seizures and is not classified as a mental health medication. 1

Pharmacological Classification and Mechanism of Action

Phenytoin is specifically classified as an antiepileptic (anticonvulsant) medication that works primarily by stabilizing neuronal membranes and inhibiting the spread of seizure activity in the motor cortex 1
The drug functions by promoting sodium efflux from neurons, which stabilizes the threshold against hyperexcitability and prevents cortical seizure foci from activating adjacent areas 1
Phenytoin reduces the activity of brain stem centers responsible for the tonic phase of tonic-clonic seizures 1

Phenytoin is indicated for the treatment of epilepsy, specifically for:
- Generalized tonic-clonic seizures 2
- Partial seizures with or without generalization 2
- Convulsive status epilepticus 3, 2
The Epilepsy Foundation of America's Working Group recommends up to 30 mg/kg of phenytoin before using another antiepileptic drug for status epilepticus 3
It is administered in various formulations including oral capsules and intravenous preparations 1

Unlike true mental health medications (antidepressants, antipsychotics, anxiolytics), phenytoin's primary mechanism and indication is neurological rather than psychiatric 1, 2
While some antiepileptic drugs have established uses in psychiatric conditions (such as carbamazepine and valproate for bipolar disorder), phenytoin is not commonly used for primary psychiatric indications in current practice 4
Although phenytoin had brief historical use for psychosis in the 1940s, it is not currently utilized as a psychiatric treatment 4

Phenytoin can affect cognition and mood as side effects rather than therapeutic targets:
- May cause cognitive impairment including slowing of thinking and motor behavior 2, 5
- Can decrease visual memory and cause motor slowing, particularly at higher serum levels 5
- May produce cerebellar symptoms as adverse effects 2
These cognitive effects are considered adverse reactions rather than therapeutic psychiatric benefits 2

When treating patients with both epilepsy and cognitive concerns, other antiepileptic medications like carbamazepine or oxcarbazepine may be preferable to phenytoin 2
Patients with epilepsy have higher rates of depression, but this is treated with actual psychiatric medications (particularly SSRIs) rather than with phenytoin 6
Long-term use of phenytoin is not recommended for patients with cognitive impairment or cerebellar symptoms 2

Therapeutic levels of phenytoin are typically between 10-20 mcg/mL, with steady-state levels achieved after 7-10 days of therapy 1
Phenytoin exhibits non-linear pharmacokinetics (saturation kinetics), meaning small dose increases can produce substantial and potentially toxic increases in serum levels 1
Regular monitoring of serum levels is essential to prevent toxicity, especially in patients with potential for drug interactions 1, 2