# A nurse reviews a serum phenytoin level of 24 mcg/mL in a client receiving the drug for tonic-clonic seizures. Which clinical findings would the nurse expect to assess?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A nurse reviews a serum phenytoin level of 24 mcg/mL in a client receiving the drug for tonic-clonic seizures. Which clinical findings would the nurse expect to assess?

## Option

1. Nystagmus, ataxia, slurred speech, and confusion **✔ Correct answer**
2. Hypertension, bradycardia, and pinpoint pupils
3. Increased salivation and bronchospasm
4. Hyperreflexia and clonus

**Correct answer: 1**

## Explanation

Correct (1): The therapeutic range is 10-20 mcg/mL. At >20: nystagmus is the earliest sign, followed by ataxia, slurred speech, and confusion. At >30-40: lethargy and coma. (2) These describe opioid toxicity. (3) Hyperreflexia/clonus suggests serotonin syndrome or hyperthyroidism. (4) Cholinergic crisis findings.

## In-depth explanation

Memory Tip Phenytoin toxicity ladder: 20+ nystagmus → 30+ ataxia → 40+ lethargy/coma. CPG Albumin-correct the level in hypoalbuminemic clients to avoid false-low reading.

## Clinical scenario

Scenario 45-year-old male on phenytoin 300 mg PO daily × 6 weeks. Trough serum level today: 24 mcg/mL (therapeutic range 10-20). He reports the room "feels wobbly."

## Key concepts

- **Therapeutic range** — Serum drug concentration that balances efficacy and toxicity; phenytoin: 10-20 mcg/mL.
- **Nystagmus** — Involuntary rhythmic eye movement; earliest clinical sign of phenytoin toxicity.
- **Narrow therapeutic index** — A small margin between therapeutic and toxic doses; phenytoin requires regular level monitoring.

## Related questions

- [A nurse is caring for an alert adult client with type 1 diabetes who reports tremors, swea…](https://mymerci.kr/pages/nclex_q.php?qn_id=360524&lang=en)
- [A 68-year-old client with COPD is admitted with shortness of breath and SpO2 86% on room a…](https://mymerci.kr/pages/nclex_q.php?qn_id=362940&lang=en)
- [A 58-year-old client arrives at the emergency department with crushing substernal chest pa…](https://mymerci.kr/pages/nclex_q.php?qn_id=362976&lang=en)
- [A 72-year-old client is brought to the emergency department by family who report that the …](https://mymerci.kr/pages/nclex_q.php?qn_id=363003&lang=en)
- [A 79-year-old client is admitted from a long-term care facility with diarrhea, decreased o…](https://mymerci.kr/pages/nclex_q.php?qn_id=363089&lang=en)
- [A 76-year-old female with chronic heart failure and atrial fibrillation receives digoxin 0…](https://mymerci.kr/pages/nclex_q.php?qn_id=374883&lang=en)
- [A 70-year-old client on long-term digoxin therapy reports new yellow-green halos around li…](https://mymerci.kr/pages/nclex_q.php?qn_id=374884&lang=en)
- [A 58-year-old client with type 2 diabetes mellitus and migraine prophylaxis is taking prop…](https://mymerci.kr/pages/nclex_q.php?qn_id=374893&lang=en)

## Read in another language

- [en](https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=en)
- [ko](https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=ko)
- [ja](https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=ja)
- [zh-TW](https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=zh-tw)
- [vi](https://mymerci.kr/pages/nclex_q.php?qn_id=391737&lang=vi)

---

More free questions: [NCLEX-RN Practice](https://mymerci.kr/pages/nclex_bank.php?lang=en)

_For study reference only. Always follow current clinical guidelines and your institution’s protocols._