Ciprofloxacin should not be given to an asthmatic using theophylline because:
**Core Concept**
Ciprofloxacin, a fluoroquinolone antibiotic, can interact with theophylline, a methylxanthine used in asthma management, due to its potential to inhibit the cytochrome P450 enzyme system, specifically CYP1A2, which is responsible for theophylline metabolism.
**Why the Correct Answer is Right**
The interaction between ciprofloxacin and theophylline can lead to increased theophylline levels, resulting in toxic effects such as nausea, vomiting, diarrhea, and in severe cases, seizures or even death. This is because ciprofloxacin competes with theophylline for the same metabolic pathway, thereby reducing theophylline's clearance and increasing its concentration in the body.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the underlying mechanism of the interaction. While it is true that ciprofloxacin can interact with theophylline, simply stating "cross-reactivity" does not provide a clear explanation.
**Option B:** Incorrect because it is too vague and does not accurately describe the specific interaction between ciprofloxacin and theophylline.
**Option C:** Incorrect because it is a distractor that does not relate to the interaction between ciprofloxacin and theophylline.
**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to be aware of the potential for fluoroquinolone antibiotics, such as ciprofloxacin, to interact with methylxanthines like theophylline, especially in patients with asthma or other respiratory conditions.
**Correct Answer:** C.