Which medication is commonly associated with nystagmus as an adverse effect?

Which medication is commonly associated with nystagmus as an adverse effect?

• A. Phenytoin
• B. Diazepam
• C. Latanoprost
• D. Tamsulosin

Answer: (A)

Nystagmus as an adverse effect is most characteristic of phenytoin among these options. Phenytoin can cause ocular motor disturbances, including nystagmus, especially as levels rise or toxicity develops. This reflects CNS effects on the cerebellar and vestibulo-ocular pathways, and nystagmus is a classic early sign that the drug’s CNS depressant effects are increasing. If nystagmus appears, it prompts checking phenytoin levels and reassessing dosing or considering alternative anticonvulsants to prevent progression to more pronounced ataxia or confusion. Diazepam can cause drowsiness and ataxia, but it does not typically produce nystagmus as a hallmark adverse effect. Latanoprost mainly causes local eye surface effects like conjunctival hyperemia and eyelash changes, not nystagmus. Tamsulosin’s common issues are orthostatic dizziness and ejaculation problems, not nystagmus.

Nystagmus as an adverse effect is most characteristic of phenytoin among these options. Phenytoin can cause ocular motor disturbances, including nystagmus, especially as levels rise or toxicity develops. This reflects CNS effects on the cerebellar and vestibulo-ocular pathways, and nystagmus is a classic early sign that the drug’s CNS depressant effects are increasing. If nystagmus appears, it prompts checking phenytoin levels and reassessing dosing or considering alternative anticonvulsants to prevent progression to more pronounced ataxia or confusion.

Diazepam can cause drowsiness and ataxia, but it does not typically produce nystagmus as a hallmark adverse effect. Latanoprost mainly causes local eye surface effects like conjunctival hyperemia and eyelash changes, not nystagmus. Tamsulosin’s common issues are orthostatic dizziness and ejaculation problems, not nystagmus.