Which symptom would not typically be expected as part of phenytoin overdose?

• A. Constipation
• B. Drowsiness
• C. Ataxia
• D. Nystagmus

Answer: (A)

Overdose from phenytoin typically produces CNS depression signs because the drug dampens neuronal excitability via sodium channel blockade. Drowsiness reflects overall sedation, ataxia comes from cerebellar involvement, and nystagmus is a classic early ocular-motor sign of toxicity. Constipation, on the other hand, does not fit the usual CNS-toxic pattern of phenytoin overdose. It’s not a hallmark feature of phenytoin toxicity, whereas the other three are commonly observed as the drug’s CNS effects worsen. In more severe cases, overdose can progress to seizures, coma, or respiratory depression, but the core acute toxicity tends to revolve around CNS depression and impaired coordination rather than bowel effects.