# Clinical context A 70-year-old client taking extended-release theophylline stopped smoking 6 days ago and started ciprofloxacin 3 days ago; repeated vomiting, tremor, agitation, an irregular heart rate of 132/min, potassium 2.9 mEq/L, and a theophylline concentration of 31 mcg/mL now suggest serious toxicity. Review the response and select the best interpretation and next plan.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=522577&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

Clinical context
A 70-year-old client taking extended-release theophylline stopped smoking 6 days ago and started ciprofloxacin 3 days ago; repeated vomiting, tremor, agitation, an irregular heart rate of 132/min, potassium 2.9 mEq/L, and a theophylline concentration of 31 mcg/mL now suggest serious toxicity.

Review the response and select the best interpretation and next plan.

| Time | Data |
| --- | --- |
| Initial evaluation | Vomiting and tremor; HR 132/min irregular; potassium 2.9 mEq/L; theophylline 31 mcg/mL |
| Early response | More alert; HR 106/min; potassium 3.5 mEq/L; theophylline 24 mcg/mL |
| Later reassessment | Vomiting recurs; frequent ventricular ectopy; theophylline 29 mcg/mL and rising |

Q1. How should the trend be interpreted?

The toxicity has permanently resolved
Sustained-release toxicity is recurring or persisting
Only the COPD is worsening

Q2. Which next plan is appropriate?

Renew urgent toxicology-directed management and continue intensive monitoring
Give the usual theophylline dose because the level fell once
Stop rhythm monitoring and discharge immediately

## Explanation

A temporary fall followed by a renewed rise in theophylline concentration, recurrent vomiting, and ventricular ectopy indicates persistent or recurrent sustained-release toxicity rather than durable clearance.

## In-depth explanation

Quick answer
Detect rebound toxicity despite early improvement.

Why this is correct
Extended-release drug can continue to be absorbed, and altered clearance remains active after one improving measurement. Serial concentrations and clinical findings must agree before monitoring is reduced.

Easy analogy or mental picture
Use a closed medication-safety loop: identify the exposure, connect the new findings, interrupt further harm, support physiology, and verify the response over time.

Memory hook
Exposure, interaction, toxicity pattern, immediate action, serial reassessment.

NCLEX decision rule
Choose the action that reduces the most immediate medication-related risk while preserving monitoring and escalation.

Why the other choices are wrong
Options that continue the exposure, treat only one symptom, or delay reassessment leave the toxic process active.References
1DailyMed: Theophylline Extended-Release TabletsNarrow therapeutic range, smoking cessation, interacting medicines, toxicity manifestations, and serial concentrations
2DailyMed: Ciprofloxacin Extended-Release TabletsCYP1A2 interaction that can increase theophylline exposure and adverse effects

## Clinical scenario

Clinical context
A 70-year-old client taking extended-release theophylline stopped smoking 6 days ago and started ciprofloxacin 3 days ago; repeated vomiting, tremor, agitation, an irregular heart rate of 132/min, potassium 2.9 mEq/L, and a theophylline concentration of 31 mcg/mL now suggest serious toxicity.

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