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Difficulty: Very hardPharmacological Therapies

A practical nurse (PN) is caring for a client with chronic bronchitis who is receiving scheduled oral theophylline. The client was also started on oral ciprofloxacin 48 hours48\text{ hours} ago for a respiratory infection. The client now reports feeling unusually restless and nauseous. Current vital signs are blood pressure 138/82 mm Hg138/82\text{ mm Hg}, heart rate 118 bpm118\text{ bpm}, and respiratory rate 20 breaths/min20\text{ breaths/min}. The morning serum theophylline level is reported as 23 mcg/mL23\text{ mcg/mL}. Based on these findings, which of the following is the most appropriate action for the PN to take?

  1. Withhold the scheduled theophylline dose and immediately notify the registered nurse (RN) of the clinical findings.Answer
  2. B
    Administer the scheduled theophylline dose with a full meal and document the laboratory results in the electronic health record.
  3. C
    Instruct the client in deep breathing and relaxation techniques to independently manage the acute restlessness.
  4. D
    Prepare to administer an intravenous (IV) push antiarrhythmic medication to rapidly stabilize the client's elevated heart rate.

Answer

The most appropriate action is to withhold the scheduled theophylline dose and immediately notify the registered nurse (RN) of the clinical findings.
The correct action demonstrates an understanding of theophylline's narrow therapeutic index (10−20 mcg/mL10-20\text{ mcg/mL}) and the interaction with ciprofloxacin, which inhibits its metabolism. The client's level of 23 mcg/mL23\text{ mcg/mL}, combined with symptoms of restlessness, nausea, and tachycardia, clearly indicates toxicity. To prevent life-threatening complications like seizures and ventricular arrhythmias, the PN must withhold the dose and promptly escalate the findings to the RN.

Step-by-Step Solution

1
Identify the normal therapeutic range for theophylline.
The therapeutic range is 10−20 mcg/mL10-20\text{ mcg/mL}.
Knowledge of narrow therapeutic index drugs is required to interpret the morning laboratory results.
2
Analyze the client's current laboratory value and clinical symptoms.
The level of 23 mcg/mL23\text{ mcg/mL} is toxic. The restlessness, nausea, and tachycardia are early clinical manifestations of this toxicity.
Connecting the objective data (lab value) with subjective/objective clinical signs (nausea, high heart rate, restlessness) confirms a systemic toxic reaction rather than simple anxiety or disease progression.
3
Identify the pharmacological cause of the toxicity.
Ciprofloxacin inhibits the CYP450 enzymatic pathway, decreasing theophylline clearance and causing serum levels to rise.
Recognizing drug-drug interactions is critical for preventing adverse events when new medications are added to a client's regimen.
4
Determine the safest action within the PN scope of practice.
The PN must safely withhold the offending agent and immediately report the life-threatening risk to the RN.
The PN is responsible for basic data collection, holding unsafe medications, and reporting abnormal/critical findings to the supervising RN for advanced intervention.

Key Concept

Theophylline toxicity, drug-drug interactions (CYP450 inhibitors), and PN scope of practice regarding critical laboratory value escalation.
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Topics

Pharmacological Therapies

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