# Clinical context: A 70-year-old client with COPD takes extended-release theophylline. The client stopped smoking 6 days ago and began ciprofloxacin 3 days ago for bronchitis. Today the client has repeated vomiting, a generalized tremor, and new agitation and confusion. Heart rate is 132/min and irregular, BP 138/84 mm Hg, RR 22/min, temperature 37.2°C (99°F), and SpO2 93% on room air. Albuterol use is unchanged at about twice daily, and there is no history of thyroid disease. Potassium is 2.9 mEq/L and the serum theophylline concentration is 31 mcg/mL. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=617380&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

Clinical context: A 70-year-old client with COPD takes extended-release theophylline. The client stopped smoking 6 days ago and began ciprofloxacin 3 days ago for bronchitis. Today the client has repeated vomiting, a generalized tremor, and new agitation and confusion. Heart rate is 132/min and irregular, BP 138/84 mm Hg, RR 22/min, temperature 37.2°C (99°F), and SpO2 93% on room air. Albuterol use is unchanged at about twice daily, and there is no history of thyroid disease. Potassium is 2.9 mEq/L and the serum theophylline concentration is 31 mcg/mL.

Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

Condition

Select 1
Thyroid storm
Theophylline toxicity
Excess beta2-agonist effect from albuterol
Nicotine withdrawal

Actions to take

Select 2
Give prescribed IV propranolol to slow the heart rate
Withhold theophylline and notify the provider now
Apply a nicotine patch to ease withdrawal agitation
Stop ciprofloxacin but give the scheduled theophylline dose on time
Start continuous cardiac monitoring with seizure precautions

Parameters to monitor

Select 2
Free thyroxine (T4) and TSH levels
Peak expiratory flow rate
Serum theophylline concentration
Oral temperature
Cardiac rhythm on telemetry

## Explanation

A level of 31 mcg/mL with vomiting, tremor, agitation, an irregular tachycardia, and hypokalemia after two clearance-lowering changes indicates theophylline toxicity. The nurse withholds theophylline, notifies the provider, and places the client on continuous cardiac monitoring with seizure precautions. The serum theophylline concentration and the cardiac rhythm show whether toxicity and its most dangerous complication are improving or worsening.

## In-depth explanation

Quick answer
Theophylline toxicity. Withhold theophylline and notify the provider; start continuous cardiac monitoring with seizure precautions. Monitor the serum theophylline concentration and the cardiac rhythm.

Why this is correct
Smoking induces CYP1A2, so stopping smoking lowers theophylline clearance, and ciprofloxacin inhibits the same enzyme. Both changes pushed the level to 31 mcg/mL, well above the usual target. Vomiting, tremor, agitation, hypokalemia, and an irregular tachycardia are classic toxic effects, and seizures and ventricular arrhythmias are the lethal complications. The drug level tells whether exposure is falling, and the rhythm tells whether the heart is still threatened.

Easy analogy or mental picture
Picture a bathtub with the tap unchanged but two drains suddenly half-plugged (no smoke, plus ciprofloxacin). The water rises even though nobody turned up the tap.

Memory hook
"Quit smoking + cipro = theo climbs." Toxic theophylline hits the gut, the heart, and the brain.

NCLEX decision rule
When a narrow-therapeutic-index drug level is high and the client is symptomatic, stop the drug and protect against its lethal complications first; then trend the drug level and the organ it threatens most.

Why the other choices are wrong
Thyroid storm shares tachycardia, tremor, agitation, and vomiting, but the normal temperature, no thyroid history, and a measured toxic drug level point elsewhere, so propranolol and a free T4 level track the wrong problem (and a nonselective beta-blocker is risky in COPD). Excess albuterol causes tremor, tachycardia, and hypokalemia, but use is unchanged, so peak flow does not measure this problem. Nicotine withdrawal explains agitation only, not vomiting, hypokalemia, or arrhythmia, and a patch does not restore the CYP1A2 induction that comes from smoke. Stopping ciprofloxacin is sensible, but giving the next theophylline dose keeps adding drug to a toxic level. Temperature is a nonspecific sign that does not track theophylline clearance.

References
1DailyMed: Theophylline extended-release prescribing informationSmoking cessation and ciprofloxacin reduce theophylline clearance; toxicity causes vomiting, tachyarrhythmias, hypokalemia, and seizures
2DailyMed: Ciprofloxacin prescribing informationCiprofloxacin inhibits CYP1A2 and raises theophylline concentrations, with reports of serious and fatal reactions

## Clinical scenario

Case update
Serious theophylline toxicity after smoking cessation and ciprofloxacin reduced drug clearance, with arrhythmia and hypokalemia.

## Key concepts

- **CYP1A2 induction** — Increased activity of a liver enzyme by tobacco smoke, which speeds theophylline breakdown; it fades within days of quitting.
- **Narrow therapeutic index** — A small gap between effective and toxic concentrations, so small clearance changes cause toxicity.
- **Seizure precautions** — Safety measures such as padded rails, suction, and oxygen at the bedside for a client at risk of seizures, as in theophylline toxicity.

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