Which antibiotics can lead to increased serum levels of theophylline?

The correct answer identifies macrolide antibiotics and ciprofloxacin as substances that can lead to increased serum levels of theophylline. This occurs due to the influence these antibiotics have on the cytochrome P450 enzyme system, particularly CYP1A2, which is responsible for metabolizing theophylline in the liver.

Macrolides, such as erythromycin and clarithromycin, are known to inhibit this enzyme, leading to reduced clearance of theophylline and subsequently higher serum concentrations. Similarly, ciprofloxacin can also inhibit CYP1A2, resulting in similar effects.

Understanding the interactions between these antibiotics and theophylline is crucial in clinical practice, especially in managing patients with respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD), where theophylline is often used for bronchodilation. Monitoring serum theophylline levels becomes important when patients are prescribed macrolides or ciprofloxacin to avoid potential toxicity due to elevated theophylline levels.

Other choices do not affect theophylline metabolism to a similar extent and therefore do not contribute to increased serum levels of the drug.