Prescribing Safety Assessment (PSA) Practice Exam

Which antiepileptic drug's common side effects include ataxia and nystagmus?

1. Sodium Valproate

2. Carbamazepine

3. Phenytoin

4. Levetiracetam

The correct answer is: Phenytoin

Phenytoin is known to be associated with specific side effects, including ataxia and nystagmus. Ataxia refers to a lack of muscle control or coordination, which can manifest as unsteadiness in walking or difficulty in performing fine motor tasks. Nystagmus, on the other hand, is characterized by rapid, uncontrollable movements of the eyes, which can affect vision and balance. These side effects occur due to the way Phenytoin influences the central nervous system, particularly through its action on voltage-gated sodium channels, which are vital in the propagation of electrical signals in the brain. The medication shifts the balance of neuronal excitability and can lead to these neurological manifestations when the serum levels of the drug are high or when a patient is sensitive to it. In contrast, while other antiepileptic drugs listed can have their own side effects, they typically do not include both ataxia and nystagmus as prominent features. For example, Sodium Valproate may cause weight gain and tremors but is less associated with nystagmus. Carbamazepine can lead to dizziness and drowsiness but lacks the same profile of eye movement disturbances. Levetiracetam is generally well-toler