When you take methadone, a long-acting opioid used for pain management and opioid use disorder. Also known as methadone hydrochloride, it helps stabilize people recovering from addiction—but it also carries a hidden risk: serious heart rhythm changes. This isn’t just a side effect you might ignore. Methadone can trigger arrhythmia, an irregular heartbeat that can lead to fainting, seizures, or sudden death, especially at higher doses or when combined with other drugs.
How does this happen? Methadone blocks a specific ion channel in heart cells called hERG. That slows down the heart’s electrical reset cycle, lengthening the QT interval on an ECG. A prolonged QT interval is the main red flag for torsades de pointes, a life-threatening type of arrhythmia linked to methadone use. It’s not rare—studies show up to 1 in 10 people on high-dose methadone develop some degree of QT prolongation. Risk goes up if you’re over 60, have heart disease, low potassium or magnesium, or are taking other drugs that affect the heart, like certain antibiotics or antidepressants.
You won’t always feel it coming. Some people get dizzy, have palpitations, or pass out. Others show no symptoms until it’s too late. That’s why doctors check your ECG before starting methadone and again after a few weeks. If you’re on methadone and suddenly feel your heart racing or skipping beats, don’t wait. Get checked. Even if you feel fine, regular monitoring is non-negotiable—especially if your dose has changed or you’ve started a new medication.
This isn’t about scare tactics. It’s about awareness. Methadone saves lives—but only if you know the risks and take steps to manage them. The posts below cover real cases, drug interactions to avoid, how labs and ECGs help catch problems early, and what alternatives exist if your heart can’t handle methadone. You’ll find practical advice from people who’ve been there, and clear guidance from medical experts who’ve studied the data. Whether you’re on methadone, caring for someone who is, or just trying to understand the risks, this collection gives you what you need to stay safe.
Methadone can prolong the QT interval, increasing the risk of life-threatening heart rhythms. Learn when to get an ECG, who’s at risk, and how to prevent sudden cardiac events while on methadone maintenance therapy.
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