QT Prolongation: What It Is, Why It Matters, and Which Medications Can Cause It

When your heart’s electrical system takes too long to reset between beats, it’s called QT prolongation, a delay in the heart’s repolarization phase that can trigger life-threatening irregular rhythms. Also known as long QT syndrome, this condition isn’t always obvious—but when it is, it can lead to torsades de pointes, a dangerous type of ventricular arrhythmia that can cause fainting, seizures, or sudden death.

Many common medications can cause QT prolongation, even in people with no prior heart problems. Drugs like certain antibiotics, antifungals, antidepressants, and even some stomach or allergy meds can slow down the heart’s electrical recovery. For example, SSRIs, a class of antidepressants, have been linked to QT changes in sensitive individuals. So have ACE inhibitors, blood pressure drugs like Enalapril, which, while generally safe, can interact with other factors like low potassium or kidney issues to raise risk. It’s not about avoiding these meds entirely—it’s about knowing your personal risk and watching for warning signs.

QT prolongation doesn’t always cause symptoms, but when it does, you might feel dizzy, have palpitations, or suddenly pass out. Doctors check for it using an ECG, where the QT interval is measured and corrected for heart rate (QTc). If your QTc is over 450 ms in men or 470 ms in women, it’s considered prolonged. Risk goes up if you’re older, have heart disease, low electrolytes, or take more than one drug that affects the QT interval. That’s why it’s so important to talk to your doctor before starting any new medication, especially if you’re already on several.

What you’ll find in the posts below isn’t just a list of drugs that can cause QT prolongation—it’s a practical guide to understanding how medications interact with your heart rhythm. You’ll see real-world examples: how GLP-1 weight-loss drugs can trigger nausea but rarely affect QT, why certain antibiotics increase yeast infection risk but also carry cardiac warnings, and how common prescriptions like Sildenafil or Perindopril fit into the bigger picture of heart safety. These aren’t theoretical concerns. People are managing these risks every day. The goal here is to help you recognize the signs, ask the right questions, and make informed choices without unnecessary fear.