Final answer:
Cimetidine is an example of a drug that could inhibit the metabolism of theophylline by the CYP450 enzyme system, potentially leading to increased side effects of theophylline.
Step-by-step explanation:
Theophylline is a substrate of the cytochrome P450 (CYP450) enzyme system, which is responsible for the metabolism of many drugs in the body. Certain drugs can inhibit or induce the function of CYP450 enzymes, altering the metabolism of substrates like theophylline. An example of a drug that could inhibit the metabolism of theophylline and potentially cause worsening of its side effects is cimetidine, which is a known CYP450 enzyme inhibitor. Other drugs, such as certain antidepressants, antifungals, and antibiotics, can have similar effects. It's important to be aware of these drug interactions to prevent adverse effects associated with increased levels of theophylline.