A patient who takes oral theophylline twice daily for chronic stable asthma develops an infection and will take ciprofloxacin. The NP should:

• A. Reduce the theophylline dose
• B. Change antibiotics to avoid interaction
• C. Switch to a LABA
• D. Change to intermittent theophylline

Answer: (A)

The key idea is a drug interaction: theophylline is cleared mainly by liver enzymes, especially CYP1A2, and ciprofloxacin strongly inhibits this pathway. When you give ciprofloxacin to a patient already taking theophylline, theophylline levels can rise quickly, pushing into toxic range because the drug has a narrow therapeutic window. To prevent toxicity while still treating the infection, the theophylline dose should be reduced and levels (and clinical signs) should be closely monitored. If feasible, choosing an antibiotic without this interaction would be preferable, but if ciprofloxacin is needed, lowering theophylline dose is the correct approach. Switching to a LABA won’t address the interaction, and intermittent theophylline would cause unstable control and further toxicity risk. Be alert for signs of theophylline toxicity such as nausea, tachycardia, tremor, or seizures, and adjust dosing accordingly.