# A patient on chronic phenytoin for seizure disorder reports new diplopia and unsteady gait. The phenytoin level is 28 mcg/mL (therapeutic 10 to 20). Which is the most appropriate nursing action?

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> language: en  
> subject: NCLEX-RN  
> category: PPT

## Question

A patient on chronic phenytoin for seizure disorder reports new diplopia and unsteady gait. The phenytoin level is 28 mcg/mL (therapeutic 10 to 20). Which is the most appropriate nursing action?

## Option

1. Continue the current dose; the symptoms are unrelated to phenytoin.
2. Hold the next dose, notify the provider, place the patient on fall precautions, and assess for nystagmus and ataxia. **✔ Correct answer**
3. Double the next dose to bring the level back into the therapeutic range faster.
4. Administer activated charcoal STAT to absorb the excess drug.

**Correct answer: 2**

## Explanation

Phenytoin therapeutic range is 10 to 20 mcg/mL. Level 28 represents toxicity. Classic toxicity findings: nystagmus (the earliest sign), diplopia, ataxia, slurred speech, confusion. Action: HOLD the dose, notify provider for dose adjustment, place on fall precautions, and complete neurologic assessment. Doubling the dose (3) is dangerous; activated charcoal (4) is not appropriate for chronic toxicity (it is used in acute overdose within ~1 hour of ingestion).

## In-depth explanation

Phenytoin levels and signs are highly testable: 10-20 therapeutic, 20-30 nystagmus + diplopia + ataxia, 30-40 lethargy, > 40 coma/seizures (paradoxically). The earliest detectable sign is horizontal nystagmus on lateral gaze — assess routinely.

## Clinical scenario

**Patient on chronic phenytoin** reports **new diplopia and unsteady gait**. Phenytoin level **28 mcg/mL** (therapeutic 10-20). Vital signs stable, no active seizing.

## Key concepts

- **Phenytoin therapeutic level** — 10-20 mcg/mL; narrow therapeutic index requires routine TDM and assessment for toxicity.
- **Phenytoin toxicity progression** — 20-30 nystagmus/diplopia/ataxia, 30-40 lethargy, > 40 coma or paradoxical seizures.
- **Routine nystagmus assessment** — Test horizontal lateral gaze at every shift in chronic phenytoin patients — earliest toxicity sign.

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