Question

Theophylline is CYP450 substrate, recent use of what drug could cause no effect of the drug?

Answer 1

Recent use of a CYP1A2 inhibitor, such as fluoroquinolone antibiotics (e.g., ciprofloxacin), antiarrhythmics, or oral contraceptives, could lead to decreased metabolism of theophylline, potentially causing elevated levels and toxicity.

Step-by-step explanation:

Theophylline is primarily metabolized by cytochrome P450 (CYP450) enzymes in the liver, particularly CYP1A2. If a drug that inhibits CYP1A2 is recently used, it could lead to decreased theophylline metabolism, potentially resulting in elevated theophylline levels and increased risk of toxicity.

Drugs such as fluoroquinolone antibiotics (e.g., ciprofloxacin), certain antiarrhythmics, and oral contraceptives are known inhibitors of CYP1A2. Therefore, their recent use might impair the normal metabolism of theophylline, causing an accumulation of the drug in the body. Monitoring theophylline levels and adjusting the dosage in the presence of such inhibitors is crucial to avoid adverse effects and ensure therapeutic efficacy.

Answer 2

A CYP450 inhibitor drug could cause no effect of theophylline by blocking its metabolism, resulting in increased levels of theophylline in the blood. Examples of CYP450 inhibitors include erythromycin and cimetidine.

Step-by-step explanation:

The drug that could cause no effect of theophylline is a CYP450 inhibitor, rather than a substrate. When a drug inhibits CYP450 enzymes, it can reduce or block the metabolism of other drugs that are substrates for the same enzyme.

For example, if a patient is taking a drug like erythromycin or cimetidine, which are known CYP450 inhibitors, and also takes theophylline, the metabolism of theophylline may be inhibited. This can lead to increased levels of theophylline in the blood, potentially causing toxic effects.

It's important for healthcare providers to be aware of potential drug interactions with theophylline and to monitor patients accordingly.