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

When your heart’s electrical cycle gets disrupted, it can lead to QT prolongation, a delay in the heart’s repolarization phase that increases the risk of dangerous irregular heartbeats. Also known as long QT syndrome, this condition doesn’t always cause symptoms—but when it does, it can trigger sudden cardiac arrest. It’s not just a rare genetic issue. More often, it’s triggered by everyday medications, especially when multiple drugs are taken together or when electrolytes like potassium and magnesium drop too low.

Many common prescriptions can stretch the QT interval, including certain antibiotics, like azithromycin and levofloxacin, which interfere with heart cell ion channels, and even some antidepressants, such as citalopram and escitalopram, known to affect cardiac rhythm. Even over-the-counter antihistamines like diphenhydramine can do it. The risk goes up if you’re older, have kidney or liver problems, or are taking more than one QT-prolonging drug at once. It’s not about avoiding meds—it’s about knowing which ones to watch for and when to ask your doctor for an ECG.

Electrolyte imbalances, especially low potassium or magnesium, make QT prolongation much more likely. That’s why vomiting, diarrhea, or diuretics can turn a safe dose into a dangerous one. People on long-term steroid therapy or those with eating disorders are at higher risk too. The good news? Most cases are reversible. Stopping the trigger drug and correcting electrolytes often brings the heart rhythm back to normal. But ignoring it? That’s when things turn critical.

What you’ll find below isn’t just a list of drugs that cause QT prolongation. It’s a practical guide to spotting the hidden risks in your medicine cabinet. From how anticoagulants interact with heart rhythm to why some herbal supplements silently affect your heart, these posts show you what to ask your pharmacist, what to watch for at home, and how to avoid being caught off guard by a side effect no one warned you about.