Which of the following is considered an adverse effect of phenytoin?

• A. Rash
• B. Drowsiness
• C. Suicidal Ideation
• D. Nystagmus

Answer: (A)

Rash is a classic adverse effect of phenytoin. Phenytoin can trigger dermatologic reactions ranging from mild rashes to serious hypersensitivity like Stevens-Johnson syndrome, which is why noticing a rash early is important and may require stopping the drug and evaluating for a serious reaction.

While other effects like drowsiness can occur, they are less specific to phenytoin and not as characteristic. Suicidal ideation is a possible risk with many antiepileptic drugs but isn’t the feature most typically associated with phenytoin in exam-style questions. Nystagmus can occur when levels are high or toxicity is present, but it’s a sign of toxicity rather than a common, widely recognized adverse effect.