# Situation: A 34-year-old woman with generalized myasthenia gravis (MG) is admitted to the medical ward with fever and a productive cough. She weighs 60 kg. She takes pyridostigmine 60 mg by mouth every 6 hours and prednisone 10 mg once daily. She has no drug allergies. Her sputum culture is pending. Which newly written order should the nurse clarify with the physician before giving it?

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> subject: Nursing Practice IV — Care of Clients with Problems in Nutrition and Gastrointestinal, Metabolism and Endocrine, Perception and Coordination

## 문제

Situation: A 34-year-old woman with generalized myasthenia gravis (MG) is admitted to the medical ward with fever and a productive cough. She weighs 60 kg. She takes pyridostigmine 60 mg by mouth every 6 hours and prednisone 10 mg once daily. She has no drug allergies.

Her sputum culture is pending. Which newly written order should the nurse clarify with the physician before giving it?

## 보기

1. Levofloxacin 750 mg intravenously once daily **✔ 정답**
2. Paracetamol 500 mg orally every 6 hours as needed
3. Ceftriaxone 1 g intravenously once daily
4. Omeprazole 20 mg orally once daily

**정답: 1**

## 해설

Fluoroquinolones such as levofloxacin carry a boxed warning because they can worsen myasthenia gravis and trigger crisis. Other drugs that impair neuromuscular transmission, such as aminoglycosides and magnesium, also need review. The nurse alerts the prescriber so a safer antibiotic can be chosen.

## 심화 해설

Why levofloxacin is the order to question

Fluoroquinolones such as levofloxacin have a boxed warning for worsening myasthenia gravis and can precipitate myasthenic crisis. The mechanism is a direct inhibition of acetylcholine release at the neuromuscular junction, which reduces the already limited postsynaptic signaling in MG. In a retrospective single-center study, fluoroquinolone use was associated with MG exacerbation, and the exacerbations occurred as early as 15 minutes to 4 days after exposure [1][4]. Postmarketing surveillance data from the US FDA Adverse Event Reporting System also support a signal linking fluoroquinolones to acute MG worsening [2].

Because this patient already has fever and a productive cough, an infection is likely driving her current weakness, but adding levofloxacin could paradoxically worsen neuromuscular transmission and push her toward respiratory failure. The nurse should therefore clarify the order before administration and request a safer alternative.

Why the other orders are acceptable

| Order | Rationale for safety in MG |
| --- | --- |
| Ceftriaxone 1 g IV once daily | Third-generation cephalosporin; no clinically significant neuromuscular blockade. Appropriate empiric coverage for community-acquired pneumonia while sputum culture is pending [3]. |
| Paracetamol 500 mg PO q6h PRN | Antipyretic with no effect on neuromuscular transmission; safe for fever management. |
| Omeprazole 20 mg PO once daily | Proton pump inhibitor used for gastric protection during prednisone therapy; no meaningful MG interaction. |

Clinical reasoning for the nurse

The patient is on pyridostigmine, a cholinesterase inhibitor, and prednisone, an immunosuppressant. Infection itself is a well-known trigger of MG exacerbation, so treating the pneumonia is essential. However, the choice of antibiotic matters. Fluoroquinolones, aminoglycosides, and intravenous magnesium are the classic drug classes to avoid or question in MG because they impair neuromuscular transmission. A macrolide such as azithromycin may also warrant caution, although the association is less consistently reported than with fluoroquinolones [1][2].

Watch out! A boxed warning means the risk is serious enough that the FDA requires prominent labeling. It does not mean the drug is absolutely contraindicated in every MG patient, but it does mean the prescriber must be alerted so the risk-benefit decision is explicit.

Key point! The nurse’s role is not to independently stop the order, but to clarify with the physician before giving levofloxacin, because a safer antibiotic such as ceftriaxone is already ordered and available for this pneumonia.References (research sources)

- [1]Frequency and Severity of Myasthenia Gravis Exacerbations Associated With the Use of Ciprofloxacin, Levofloxacin, and Azithromycin.Research articleUysal SP, Li Y, Thompson NR, Li Y. (2025) · DOI: 10.1002/mus.28410

- [2]Fluoroquinolone-associated myasthenia gravis exacerbation: evaluation of postmarketing reports from the US FDA adverse event reporting system and a literature review.Research articleJones SC, Sorbello A, Boucher RM (2011) · DOI: 10.2165/11593110-000000000-00000

- [3]Myasthenia gravis and community-acquired pneumonia: therapeutic challenges.Research articleChen X, Ding J, Zhang J, Dai H, Yu L. (2025) · DOI: 10.3389/fphar.2025.1695526

- [4][Fluoroquinolone associated myasthenia gravis exacerbation: clinical analysis of 9 cases].Research articleWang SH, Xie YC, Jiang B, Zhang JY, Qu Y, Zhao Y (2013)

## 임상 시나리오

Fluoroquinolone Use in Myasthenia GravisBoxed Warning and Nursing Action
Fluoroquinolones such as levofloxacin carry an FDA boxed warning for worsening myasthenia gravis and may precipitate myasthenic crisis. The mechanism is direct inhibition of acetylcholine release at the neuromuscular junction.

Exacerbation can occur as early as 15 minutes to 4 days after exposure. In a patient with active infection, adding levofloxacin may paradoxically worsen weakness and progress to respiratory failure.

Safer empiric alternatives for community-acquired pneumonia include ceftriaxone, a third-generation cephalosporin with no clinically significant neuromuscular blockade. Paracetamol and omeprazole are also safe in MG.

CautionBefore administering any newly ordered fluoroquinolone to an MG patient, clarify with the prescriber and request a safer antibiotic. Also review other drugs that impair neuromuscular transmission, including aminoglycosides and magnesium.

## 핵심 개념

- **Myasthenic Crisis** — Acute worsening of MG causing respiratory failure, often triggered by infection or certain drugs.
- **Fluoroquinolone Boxed Warning** — FDA warning that fluoroquinolones can worsen MG by inhibiting acetylcholine release at the neuromuscular junction.
- **Neuromuscular Junction** — Synapse where motor neurons release acetylcholine to activate muscle contraction; impaired in MG.
- **Pyridostigmine** — Acetylcholinesterase inhibitor that increases acetylcholine availability at the neuromuscular junction in MG.
- **Empiric Antibiotic** — Initial antibiotic chosen before culture results are available, based on likely pathogens.

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