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Increased theophylline concentrations secondary to ciprofloxacin
M J Rybak1, S K Bowles, P H Chandrasekar
1Department of Pharmacy Services, Detroit Receiving Hospital, University Health Center, MI 48021.
Abstract:
An 82-year-old man with a history of myasthenia gravis and heart failure was admitted to the hospital with respiratory failure. Aminophylline and eventually theophylline therapy were initiated to improve respiratory status. During the hospital stay, the patient developed a resistant pseudomonal pneumonia. After failure with conventional antibiotics, ciprofloxacin was initiated because of favorable sensitivity and the planned avoidance of aminoglycoside therapy. Seventy-two hours after initiation of ciprofloxacin, the patient's theophylline level rose from a steady-state baseline of 9.8 micrograms/ml to 34.7 micrograms/ml. After the theophylline dose was reduced by approximately 67 percent, the patient's theophylline serum concentration returned to baseline (10 micrograms/ml). Until more data concerning the interaction of theophylline and ciprofloxacin are available, we recommend close monitoring of theophylline serum concentrations in patients receiving concomitant ciprofloxacin.
Insights
Ciprofloxacin can significantly increase theophylline levels in patients, potentially causing toxicity. Close monitoring of theophylline serum concentrations is recommended when these drugs are used together.
Area of Science:
- Pharmacology
- Clinical Medicine
Background:
- Theophylline is a bronchodilator used for respiratory conditions.
- Ciprofloxacin is a broad-spectrum antibiotic.
- Drug interactions can alter medication efficacy and safety.
Observation:
- A patient receiving theophylline therapy was initiated on ciprofloxacin for pseudomonal pneumonia.
- Theophylline serum levels increased dramatically after starting ciprofloxacin.
- Reducing the theophylline dose normalized serum concentrations.
Findings:
- Ciprofloxacin significantly inhibited the metabolism of theophylline.
- This drug interaction led to a potentially toxic increase in theophylline levels.
- The interaction highlights the importance of therapeutic drug monitoring.
Implications:
- Clinicians should closely monitor theophylline serum concentrations in patients concurrently treated with ciprofloxacin.
- Further research is needed to fully elucidate the pharmacokinetic interaction between theophylline and ciprofloxacin.
- This interaction may necessitate dose adjustments for theophylline to prevent adverse events.