QT Prolongation: Risks, Causes, and Medications That Can Trigger It

When your heart’s electrical cycle takes too long to reset after a beat, it’s called QT prolongation, a delay in the heart’s repolarization phase that can lead to life-threatening irregular rhythms. Also known as long QT syndrome, it’s not always genetic—often, it’s triggered by the very medicines people take every day. This isn’t just a lab number. It’s a real risk that can flip a routine prescription into a cardiac emergency.

Many common drugs—antibiotics, antidepressants, antifungals, even some anti-nausea meds—can interfere with the heart’s ion channels and stretch out the QT interval. Torsades de pointes, a specific type of dangerous heart rhythm that can lead to sudden cardiac arrest is the most feared outcome. It doesn’t always come with warning signs. Some people feel dizzy or faint, others have no symptoms at all until it’s too late. Risk goes up if you’re also low on potassium or magnesium, have kidney or liver problems, or take more than one drug that affects the QT interval. That’s why doctors check your meds before prescribing, especially if you’re older or on multiple prescriptions.

Electrolyte imbalance, a drop in potassium, magnesium, or calcium levels that disrupts normal heart signaling is a major player too. Diuretics, vomiting, or poor nutrition can create this perfect storm. And while some people are born with long QT syndrome, most cases seen in clinics are acquired—often from drug interactions. The problem is, many of these drugs are sold over the counter or prescribed without a full cardiac review. A simple ECG can catch it early, but too often, it’s missed until after the fact.

What you’ll find in the posts below isn’t just a list of drugs. It’s a practical look at how everyday medications like Azithromycin, Doxylamine, and even some pain relievers can quietly stretch your heart’s rhythm. You’ll see comparisons between similar drugs, how side effects stack up, and which combinations to avoid. Whether you’re managing chronic pain, sleep issues, or heart conditions, these posts help you spot the hidden risks before they become emergencies.