Theophylline metabolism interaction with ciprofloxacin
**Core Concept**
Theophylline is a methylxanthine medication used to treat asthma and COPD. Its metabolism is primarily through the cytochrome P450 enzyme CYP1A2 in the liver. Ciprofloxacin, a fluoroquinolone antibiotic, is known to inhibit this enzyme, leading to increased theophylline levels and potential toxicity.
**Why the Correct Answer is Right**
Ciprofloxacin inhibits the CYP1A2 enzyme, which is responsible for theophylline metabolism. This leads to decreased theophylline clearance and increased serum concentrations, potentially causing toxicity such as seizures, arrhythmias, and even death. The interaction between ciprofloxacin and theophylline is a well-documented pharmacokinetic interaction that can have significant clinical implications.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of the interaction between ciprofloxacin and theophylline. Ciprofloxacin does not induce the CYP1A2 enzyme, but rather inhibits it.
**Option B:** This option is incorrect because it suggests that ciprofloxacin increases theophylline metabolism, which is the opposite of what actually occurs. Ciprofloxacin inhibition of CYP1A2 leads to decreased theophylline clearance.
**Option C:** This option is incorrect because it does not specify the enzyme involved in theophylline metabolism or the effect of ciprofloxacin on that enzyme. While ciprofloxacin does interact with multiple enzymes, its primary interaction with theophylline is through CYP1A2 inhibition.
**Clinical Pearl / High-Yield Fact**
When prescribing ciprofloxacin to patients taking theophylline, it is essential to monitor theophylline levels closely and adjust the dose accordingly to prevent toxicity. A simple mnemonic to remember this interaction is "Cipro floxacin inhibits theophylline's metabolism."
**Correct Answer:** B. Ciprofloxacin decreases theophylline clearance by inhibiting the CYP1A2 enzyme.