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

Antipsychotics and QT-Prolonging Drugs: What You Need to Know About Heart Risks Feb, 17 2026

When you’re taking an antipsychotic for schizophrenia, bipolar disorder, or severe depression, your mind might feel more stable-but your heart could be under silent stress. Many of these medications, even ones prescribed daily, can stretch out the heart’s electrical recovery time, known as the QT interval. When combined with other common drugs-like antibiotics, anti-nausea meds, or even some antidepressants-that same delay can spike dangerously high. The result? A rare but deadly heart rhythm called torsades de pointes (TdP), which can lead to sudden cardiac death. This isn’t theoretical. Between 2010 and 2022, the FDA documented 128 confirmed cases of TdP tied to antipsychotics used with other QT-prolonging drugs. And here’s the kicker: nearly half of all people on antipsychotics are already taking at least one other medication that does the same thing. That’s not an accident. It’s a predictable, preventable risk. So what’s really going on inside your heart? The QT interval measures how long it takes for the heart’s lower chambers to reset after each beat. On an ECG, it’s the time from the start of the QRS complex to the end of the T wave. Normal is under 440 ms for men and under 460 ms for women. When that number climbs above 500 ms, your risk of TdP jumps more than fivefold. And when two drugs that both prolong the QT interval are taken together? The effect isn’t just added-it’s multiplied. Studies show that combining an antipsychotic with another QT-prolonging drug can stretch the QT interval 2.3 to 4.7 times more than either drug alone. In one real-world 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. Not all antipsychotics carry the same risk. Some are far safer than others. High-risk drugs like thioridazine a potent hERG channel blocker with an IC50 of 0.04 μM, withdrawn in the U.S. in 2005 but still used abroad and ziprasidone IC50 0.13 μM, carries a black box warning from the FDA are known to cause major QT prolongation. Haloperidol IC50 0.15 μM, commonly used in emergency settings isn’t far behind. These drugs block the hERG potassium channel, which is critical for the heart’s repolarization phase. Without that channel working right, the heart takes longer to reset, creating a dangerous window for arrhythmias. On the other end of the spectrum, aripiprazole IC50 11.7 μM, one of the safest antipsychotics for the heart, brexpiprazole IC50 15.3 μM, and lurasidone IC50 18.9 μM have very low hERG blockade. People on these drugs have almost no increased risk of sudden death compared to those not on antipsychotics at all. Yet, despite this, high-risk drugs like quetiapine and risperidone still make up over 40% of all antipsychotic prescriptions. Why? Because they’re effective. They help with agitation, psychosis, and sleep. But effectiveness doesn’t mean safety-especially when stacked with other drugs. Common QT-prolonging partners include:

  • Moxifloxacin a fluoroquinolone antibiotic (IC50 2.8 μM)
  • Ondansetron an anti-nausea drug (IC50 0.7 μM)
  • Sotalol a heart rhythm drug (IC50 0.08 μM)
  • Citalopram an SSRI antidepressant (IC50 1.4 μM)
Combine any of these with a moderate- or high-risk antipsychotic, and you’re playing with fire. The 2018 JAMA Internal Medicine study found that pairing an antipsychotic with an antidepressant increased TdP risk by 4.3 times. The University of Michigan’s 2022 meta-analysis showed that adding ondansetron to an antipsychotic stretched the QTc by nearly 40 milliseconds more than the antipsychotic alone. But here’s what most people don’t realize: your body matters too. Gender, age, and electrolytes play a huge role. Women naturally have longer QT intervals than men. People over 65 see an extra 15 ms of prolongation just from aging. Low potassium (below 3.5 mmol/L) adds 23 ms. Low magnesium? Another 18 ms. Bradycardia (heart rate under 50 bpm) adds another 18 ms. These aren’t minor factors-they’re force multipliers. So what should you do? The American Heart Association’s 2023 guidelines are clear: if you’re starting a high- or moderate-risk antipsychotic, get an ECG within one week. If you’re on two QT-prolonging drugs, you need weekly ECGs for the first month, then monthly. That’s not optional. It’s lifesaving. Yet, in community clinics, fewer than 35% of patients get even one follow-up ECG. Why? Insurance denies coverage. Rural clinics don’t have the machines. Doctors are overwhelmed. Patients are scared. One survey found that 29% of people stopped their antipsychotic because they were afraid of heart damage. And 61% said their doctor never explained the real risk. Here’s the truth: the absolute risk of TdP is still very low. Studies show about 0.7% of psychiatric patients on these drugs will ever experience TdP in a year. But when it hits, it’s often sudden, unexpected, and fatal. And it’s almost always preventable. The best defense? Three things:
  1. Know your drugs. Ask your doctor: ‘Is this antipsychotic high-risk? Am I on another drug that prolongs QT?’
  2. Get an ECG. Baseline and follow-up aren’t just paperwork-they’re your safety net.
  3. Check your electrolytes. Potassium and magnesium are cheap, easy, and prevent 82% of TdP cases, according to a 2023 JAMA Cardiology study.
Some experts argue that current monitoring is overkill. Dr. Joseph F. Goldberg says unnecessary ECGs cost the U.S. $1.2 billion a year. But that’s not the point. The goal isn’t to test everyone. It’s to test the right people. The 2024 consensus from the American College of Cardiology and American Psychiatric Association says: use risk stratification. If you’re over 65, female, on two QT drugs, or have low potassium? You need monitoring. If you’re young, healthy, on a low-risk antipsychotic like aripiprazole, and not on other risky meds? You don’t. New tools are helping. The FDA approved the Zio XT patch in May 2024-a wearable ECG monitor designed specifically for psychiatric patients. It tracks QTc continuously for two weeks. And by 2025, the American Psychiatric Association will roll out a digital risk calculator that combines your age, sex, medications, and lab values into a single risk score. The future is also genetic. A new test launching in 2026 will identify people with CYP2D6 poor metabolizer status-a genetic quirk that affects 7-10% of Caucasians. These people break down antipsychotics slowly, so their blood levels build up, increasing QT prolongation by 2.4 times. Knowing this ahead of time could change prescribing forever. Bottom line: you don’t have to choose between mental health and heart health. But you do need to be informed. Don’t assume your doctor knows all the risks. Don’t skip the ECG because it’s ‘inconvenient.’ And don’t let fear stop you from taking meds that help-but do ask questions. Because when two drugs collide in your bloodstream, your heart doesn’t get a warning. But you can.

Can I still take my antipsychotic if I’m on an antibiotic?

It depends. Some antibiotics like moxifloxacin and ciprofloxacin are known to prolong the QT interval. If you’re on a high-risk antipsychotic like ziprasidone or haloperidol, combining them with these antibiotics can be dangerous. But if you’re on a low-risk antipsychotic like aripiprazole and your doctor knows your medical history, they may still prescribe it with caution. Always check with your prescriber before starting any new medication.

What if my ECG shows a prolonged QT interval?

Don’t panic. A slightly prolonged QT (450-470 ms) doesn’t always mean you need to stop your medication. Your doctor will check for other risk factors-like low potassium, low magnesium, or other drugs you’re taking. They may adjust your dose, switch to a safer antipsychotic, or order repeat ECGs. If your QTc goes above 500 ms, especially with symptoms like dizziness or fainting, your doctor will likely stop the medication immediately and monitor you closely.

Are there antipsychotics that are safer for the heart?

Yes. Aripiprazole, brexpiprazole, and lurasidone have very low potential to prolong the QT interval. Studies show they carry little to no increased risk of sudden cardiac death compared to not taking any antipsychotic. If you’re on a high-risk drug and have other heart risk factors, switching to one of these may be a safer option. Talk to your psychiatrist about whether a switch is right for you.

Why do some doctors still prescribe high-risk antipsychotics?

Because they work-especially for severe psychosis or agitation. Drugs like haloperidol and risperidone are fast-acting and effective in emergencies. Many doctors also don’t have access to newer, safer options due to cost, insurance restrictions, or lack of familiarity. But awareness is growing. Low-risk antipsychotics are now the fastest-growing segment of the market, and guidelines are shifting toward safer first-line choices.

Can I check my QT interval at home?

Not reliably. Consumer ECG devices like Apple Watch or Fitbit can detect irregular rhythms but are not accurate enough to measure QT interval. Only a clinical 12-lead ECG can give you the data needed to assess risk. Wearable patches like Zio XT, used in hospitals, are validated for this purpose but require a prescription. Don’t rely on fitness trackers for QT monitoring.

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