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

When your heart’s electrical cycle takes too long to reset, it’s called QT prolongation, a delay in the heart’s repolarization phase that can lead to irregular heartbeats. Also known as long QT syndrome, it’s not always genetic — often, it’s caused by the very drugs you take to feel better.

Many common medications — from antibiotics and antidepressants to anti-nausea pills and heart drugs — can interfere with your heart’s rhythm. Torsades de pointes, a life-threatening type of irregular heartbeat linked directly to QT prolongation doesn’t happen often, but when it does, it can cause fainting, seizures, or sudden death. People with kidney problems, low potassium or magnesium, or those taking multiple drugs at once are at higher risk. Even something as simple as skipping a meal or overdoing caffeine can tip the balance if you’re already on a risky medication.

It’s not just about the drug itself — it’s about how it interacts with your body. For example, antidepressants like paroxetine, used to treat anxiety and depression, can lengthen the QT interval, especially at higher doses. Same with antibiotics like cephalexin, a common treatment for infections, or even anti-nausea drugs, often prescribed during pregnancy or after surgery. These aren’t rare side effects — they’re documented, predictable, and often avoidable if you know what to look for.

Doctors don’t always check your QT interval unless you have symptoms or are on multiple high-risk drugs. But if you’ve ever felt your heart skip, flutter, or race out of nowhere — especially after starting a new medication — that’s not normal. It could be your body signaling a problem. Tracking your meds, knowing your electrolyte levels, and asking your pharmacist or doctor about drug interactions can make all the difference.

Below, you’ll find real-world examples of how medications interact with your heart’s rhythm, what to watch for, and how to avoid dangerous combinations. Whether you’re managing anxiety, diabetes, infections, or chronic pain, understanding QT prolongation could help you stay safe — and maybe even save your life.