Antipsychotics and QT-Prolonging Drugs: What You Need to Know About Heart Risks

When you take an antipsychotic for schizophrenia, bipolar disorder, or severe depression, your doctor focuses on calming your mind. But there’s another system in your body that’s quietly at risk: your heart. Many of these medications don’t just affect dopamine and serotonin-they also interfere with the electrical rhythm of your heart. And when you add another drug that does the same thing, the danger multiplies. This isn’t theoretical. It’s happening in real patients, sometimes with deadly results.

What QT Prolongation Really Means

Your heart beats because of electrical signals. The QT interval on an ECG measures how long it takes for your heart’s lower chambers to recharge after each beat. If that time gets too long-past 450 ms in men, 460 ms in women-you’re at risk for a dangerous rhythm called torsades de pointes. It’s not a heart attack. It’s a chaotic, fast fluttering that can turn into sudden cardiac death if not caught fast.

This isn’t new. French doctor Dessertenne first described torsades de pointes in 1966, linking it to early antipsychotics. Today, about 70% of commonly prescribed antipsychotics have this effect. It happens because they block the hERG potassium channel-a key player in resetting the heart’s electrical charge. Block that channel, and the heart takes longer to recover. Simple. Dangerous.

Which Antipsychotics Are Riskiest?

Not all antipsychotics are created equal when it comes to heart risk. The data is clear:

• High risk: Thioridazine (withdrawn in the U.S. but still used elsewhere), ziprasidone, haloperidol. These have IC50 values under 1 μM-meaning they block hERG at very low concentrations.
• Moderate risk: Quetiapine, risperidone, olanzapine. These are widely prescribed, but their hERG blockade is stronger than many realize.
• Low risk: Aripiprazole, brexpiprazole, lurasidone. These have IC50 values above 10 μM, making them much safer for the heart.

Here’s the problem: the most commonly prescribed antipsychotics are the moderate-risk ones. Quetiapine alone was filled over 24 million times in 2023. Risperidone? Nearly 18.3 million. Meanwhile, low-risk options like aripiprazole are growing-but slowly.

When Two Dangerous Drugs Combine

The real danger isn’t just one antipsychotic. It’s what you take with it.

Antidepressants like citalopram, antibiotics like moxifloxacin, anti-nausea drugs like ondansetron, and even some heart rhythm meds like sotalol all prolong the QT interval. When you stack them with an antipsychotic, the effect isn’t just added-it’s multiplied.

A 2021 study from the University of Pennsylvania found that combining antipsychotics with other QT-prolonging drugs caused QTc prolongation that was 2.3 to 4.7 times worse than taking either drug alone. In one documented case, a 68-year-old woman on quetiapine and ciprofloxacin saw her QTc jump from 448 ms to 582 ms in just 72 hours. She nearly died.

The 2018 JAMA Internal Medicine study showed that pairing antipsychotics with antidepressants increased torsades risk by 4.3 times. Add an antiemetic like ondansetron? QTc increases by nearly 39 milliseconds-more than double the rise from the antipsychotic alone.

Who’s Most at Risk?

It’s not just the drugs. Your body matters too.

• Age over 65: Adds 15.3 ms to QTc
• Female sex: Adds 12.8 ms
• Low potassium (below 3.5 mmol/L): Adds 22.7 ms
• Slow heart rate (under 50 bpm): Adds 18.4 ms

Put those together-say, a 70-year-old woman on quetiapine with low potassium and a UTI treated with moxifloxacin-and you’re looking at a QTc that could spike past 500 ms. That’s a five-fold increase in torsades risk.

And here’s the kicker: 45% of people on antipsychotics are already taking at least one other QT-prolonging drug. Most don’t know it. Many doctors don’t either.

What Should You Do?

You don’t need to stop your meds. But you do need to be proactive.

Baseline ECG: Get one before starting any moderate- or high-risk antipsychotic. Do it within a week. The American Heart Association says so.

Follow-up ECGs: If you’re on a high-risk combo (like ziprasidone plus ondansetron), get an ECG weekly for the first month, then monthly. For moderate-risk alone, check at 1 week, 4 weeks, then every 3 months.

Check your electrolytes: Low potassium and magnesium are silent triggers. Ask for a simple blood test. Dr. Jonathan Troxel’s 2023 study showed electrolyte monitoring prevents 82% of torsades cases in polypharmacy patients.

Ask your pharmacist: Not all doctors track every drug interaction. Pharmacists have tools that flag QT risks across your entire med list. Use them.

Why Are So Many People Still at Risk?

Because the system is broken.

Only 35% of community clinics routinely do ECG monitoring-even though guidelines have been clear for years. Why? Insurance denies coverage. Rural clinics don’t have ECG machines. Doctors are rushed. Patients are scared.

A 2023 NAMI survey found that 29% of patients stopped their antipsychotic because they feared heart problems. But 61% said their doctor never explained the actual risk level. That’s not fear-it’s ignorance.

Meanwhile, a 2022 review estimated that unnecessary ECGs cost the U.S. $1.2 billion a year. But cutting monitoring isn’t the answer. The goal is smart monitoring-targeted, evidence-based, and personalized.

The Future Is Changing

Change is coming. The FDA approved the Zio XT patch in May 2024-a wearable ECG monitor designed specifically for psychiatric patients. It’s small, comfortable, and detects QTc over 500 ms with 98.7% accuracy.

By January 2025, the American Psychiatric Association will release new guidelines with a digital risk calculator. It will factor in your age, sex, meds, electrolytes, and even genetics. A new test launching in 2026 will identify if you’re a CYP2D6 poor metabolizer-a genetic group that processes antipsychotics slowly, leading to dangerous buildup.

Medicare is starting to tie payments to monitoring compliance. By 2027, low-risk antipsychotics are expected to make up over half of new prescriptions. The market is shifting because the science is clear: safety works.

Bottom Line

You don’t have to choose between mental health and heart health. But you do have to be informed. If you’re on an antipsychotic, ask: Is this the safest option for me? Am I taking anything else that could hurt my heart? Have I had an ECG? Are my potassium and magnesium levels checked?

The risk is real. But it’s manageable. With the right checks, the chance of torsades drops to less than 1 in 100,000 patient-years. That’s not zero-but it’s close enough to let you live well, safely, and without fear.