Dados do Trabalho

Título

Phenytoin Induced Dyskinesia: a rare and underrecognized adverse event

Apresentação do caso

A 61-year-old male with a medical history of cognitive impairment and epilepsy was brought to the emergency department due to a history of generalized tonic-clonic seizures after his anti-seizure medications (ASM) adjustment - at the time, he was using phenytoin 100mg 12/12h (reduced on his own from 100mg 8/8h due to sedation and abnormal movements) and valproic acid 500mg 12/12h. After one month under this regimen, the patient noticed the appearance of repetitive and involuntary movements in the face and upper limbs, fleeting and unpredictable, which were classified as dyskinesia. A gradual reduction in phenytoin (50mg every 3 days) concomitantly with levetiracetam titration up to 500mg 12/12h, along 14 days, resulted in complete resolution of dyskinesia and adequate seizure control.

Discussão

Phenytoin, an ASM that acts by blocking voltage-gated sodium channels, is used in the treatment of epileptic seizures and status epilepticus. Its most common side effects include ataxia, brain atrophy, headache, insomnia, confusion, neuropathy and vertigo. The onset of abnormal and repetitive movements after the introduction of phenytoin, as well as his improvement after drug withdrawal, draws attention to its rare but peculiar side effect: dyskinesia. Long-term or high-dose phenytoin is believed to enhance dopaminergic and serotonergic pathways in the brain, which may play a role in the development of dyskinesia.

Comentários finais

Phenytoin induced dyskinesia, although rare, can have a great negative impact on patients' quality of life, due to both disabling involuntary movements and limiting seizure control. Knowing how to properly identify and manage this adverse event, often little recognized by physicians, can bring great benefit to patients and their families.