QT Prolongation: Risks, Medications, and What You Need to Know

When your heart’s electrical rhythm gets disrupted, QT prolongation, a delay in the heart’s repolarization phase that can lead to dangerous irregular heartbeats. Also known as long QT syndrome, it’s not always genetic—often, it’s triggered by everyday medications. This isn’t just a lab result; it’s a real risk that can lead to torsades de pointes, a life-threatening type of ventricular arrhythmia, especially if you’re on multiple drugs or have other health issues.

Many common drugs—antibiotics, antidepressants, antifungals, and even some heart meds—can stretch out the QT interval. For example, bempedoic acid, a cholesterol-lowering drug used when statins fail, carries a known risk of tendon issues and may also affect heart rhythm. Same goes for fluconazole, an antifungal that can interfere with heart electrical activity, especially when mixed with other QT-prolonging drugs. Even something as simple as an antihistamine like cetirizine (Zyrtec) can add up when combined with other meds. The problem isn’t always the drug alone—it’s the combo. Insurers and doctors use formularies and P&T committees to manage these risks, but patients often don’t know what’s in their own pill bottle.

If you’re on more than one prescription, have a history of heart problems, or take supplements, you’re at higher risk. QT prolongation doesn’t always cause symptoms, but when it does, it’s sudden: dizziness, fainting, or a racing heartbeat. The good news? It’s often preventable. Doctors can check your EKG, review your meds, and swap out risky combinations before anything happens. Below, you’ll find real-world breakdowns of drugs that affect heart rhythm, how they interact with each other, and what steps you can take to protect yourself—without needing a medical degree.