# A client on chronic theophylline is given a new prescription for ciprofloxacin to treat a UTI. Which is the nurse's priority action?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=391784&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A client on chronic theophylline is given a new prescription for ciprofloxacin to treat a UTI. Which is the nurse's priority action?

## Option

1. Instruct the client to take the ciprofloxacin with an antacid to improve absorption and minimize gastrointestinal upset, as food interactions are common with fluoroquinolones.
2. Administer both medications as prescribed, as there is no known interaction between theophylline and ciprofloxacin that requires dose adjustment.
3. Notify the provider — ciprofloxacin is a strong CYP1A2 inhibitor and increases theophylline levels; an alternative antibiotic or theophylline dose adjustment is needed **✔ Correct answer**
4. Discontinue theophylline permanently, because combining it with ciprofloxacin significantly increases the risk of theophylline toxicity.

**Correct answer: 3**

## Explanation

Correct (2): Ciprofloxacin is a potent CYP1A2 inhibitor that raises theophylline levels into the toxic range, causing seizures and arrhythmias. Use an alternative non-quinolone (or non-1A2-inhibiting) antibiotic, or reduce theophylline dose with close level monitoring. (1) Dangerous. (3) Antacids reduce ciprofloxacin absorption. (4) Theophylline is not permanently stopped without indication.

## In-depth explanation

Memory Tip Theophylline + Ciprofloxacin = level UP. Other 1A2 inhibitors: erythromycin, fluvoxamine, oral contraceptives (modest). Always cross-check level when adding interacting drugs.

## Clinical scenario

Scenario 60-year-old female on stable theophylline 200 mg BID for asthma. ED provider prescribes ciprofloxacin 500 mg PO BID × 7 days for a UTI.

## Key concepts

- **CYP1A2 inhibitor** — Drugs slowing CYP1A2 metabolism — ciprofloxacin, erythromycin, fluvoxamine.
- **Theophylline drug interactions** — Levels rise with CYP1A2 inhibitors, fall with CYP1A2 inducers; check at 5-7 days after change.
- **Antibiotic substitution** — Choose alternative when interacting agent risk outweighs benefit; e.g., nitrofurantoin or cephalexin for UTI.

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