Which of the following drugs, if given with terfena dine, can cause ventricular arrhythmias
## **Core Concept**
The question tests the understanding of drug interactions, specifically the risk of ventricular arrhythmias when terfenadine is co-administered with certain medications. Terfenadine is a second-generation antihistamine that can prolong the QT interval, a measure of the time it takes for the heart's ventricles to prepare for a new beat. This prolongation can predispose to serious arrhythmias, particularly Torsades de Pointes.
## **Why the Correct Answer is Right**
The correct answer, , is likely a potent inhibitor of the cytochrome P450 3A4 (CYP3A4) enzyme. Terfenadine is metabolized by CYP3A4 to its active metabolite. When a CYP3A4 inhibitor is co-administered with terfenadine, it can lead to elevated terfenadine levels, causing an excessive prolongation of the QT interval and increasing the risk of ventricular arrhythmias, such as Torsades de Pointes. This interaction is a classic example of a pharmacokinetic drug interaction leading to a significant adverse effect.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, presumably, it does not significantly inhibit CYP3A4 or does not cause a clinically relevant interaction with terfenadine that would lead to ventricular arrhythmias.
- **Option B:** This option is incorrect for similar reasons as Option A; it might not be a potent enough CYP3A4 inhibitor or might not interact with terfenadine in a way that significantly increases the risk of arrhythmias.
- **Option D:** This option is incorrect as it might not have a significant effect on the CYP3A4 enzyme or on terfenadine levels.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that terfenadine was withdrawn from many markets due to its potential to cause serious cardiac arrhythmias, particularly when taken with CYP3A4 inhibitors or in patients with hepatic impairment. This highlights the importance of understanding drug interactions and the potential for certain drugs to cause QT interval prolongation.
## **Correct Answer:** . Erythromycin