7 QT-Prolonging Drugs: How These Medications Can Affect Heart Rhythms

In the 1990s and early 2000s, several medications were removed from the market because of a risk for life-threatening arrhythmias (abnormal heart rhythms). The arrhythmias were caused by a side effect called QT prolongation.

Since then, the FDA has required new medications to undergo separate safety studies for this side effect. But even with this testing, there are still close to 200 QT-prolonging drugs on the market.

What is QT prolongation?

QT prolongation, also called long QT syndrome, is a type of arrhythmia. It happens when the natural electrical system in your heart is disrupted. Normally, electrical pulses keep our heart beating at a steady, regular rhythm. In long QT syndrome it takes longer for the heart to recharge itself between each beat.

“Long QT” refers to how this condition looks on an electrocardiogram (EKG). An EKG maps each heartbeat as five separate electrical waves: P, Q, R, S, and T. If you have QT prolongation, there is a longer space between the Q and T waves on your EKG results.

What are the symptoms of QT prolongation?

Having a long QT interval can disrupt the heart’s natural rhythm. It may cause fast, uncontrollable heartbeats. This can sometimes become life-threatening.

Some people have no symptoms with QT prolongation. Others can experience symptoms, including:

• Palpitations (flutters in the chest)

• Tiredness or weakness

• Gasping during sleep

• Dizziness

• Fainting

• Seizures

• Sudden cardiac arrest (when your heart suddenly stops)

Is QT prolongation dangerous?

Yes. QT prolongation can become dangerous. And medications are the most common cause of long QT syndrome. So it’s good to know if you’re taking something that increases your risk. Below, we detail seven types of QT-prolonging drugs, plus other notable medications.

Good to know: Even though these medications can cause QT prolongation, it’s a rare side effect for most people. Your prescriber will assess your risk of long QT syndrome and monitor you more closely if needed. Always talk with a healthcare professional before stopping or adjusting any medications.

1. Antiarrhythmics, such as amiodarone

Antiarrhythmics are medications that treat irregular heartbeats. They are used for heart conditions such as atrial fibrillation and ventricular arrhythmias. Antiarrhythmics include medications like:

• Amiodarone (Pacerone)

• Dofetilide (Tikosyn)

• Flecainide

• Quinidine

• Sotalol (Betapace)

Most medications that help control heart rhythm affect the heart’s electrical system, including the QT interval. This makes antiarrhythmics the type of medication most likely to cause QT prolongation. Of this group, quinidine has the most potential to cause arrhythmias.

EXPERT PICKS: WHAT TO READ NEXT

• Who’s at risk for long QT syndrome? Read about how healthcare professionals assess your risk for QT prolongation.

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• What causes interactions? QT prolongation is a serious complication that can happen when medications interact. Read more about why drug interactions happen.

If you’ve been prescribed an antiarrhythmic, a cardiologist (heart specialist) should closely monitor your heart health and EKG. Be sure to report any new or worsening symptoms to them right away.

2. Macrolide antibiotics, such as azithromycin

Macrolide antibiotics treat a variety of bacterial infections. These include sinus, respiratory, and skin infections. They usually have “-omycin” at the end of their generic name. Examples of common macrolide antibiotics are:

• Azithromycin (Zithromax)

• Clarithromycin

• Erythromycin (Ery-Tab)

Some studies suggest that macrolides are the antibiotic class with the greatest risk of QT prolongation. There are more reports of long QT and arrhythmias with macrolides compared with other types of antibiotics.

3. Quinolone antibiotics, such as ciprofloxacin

Fluoroquinolone antibiotics (“quinolones”) treat several types of infections. These include urinary tract infections and certain types of pneumonia. They usually have “-floxacin” at the end of their generic name.

Examples of quinolones include:

• Ciprofloxacin (Cipro)

• Levofloxacin

• Moxifloxacin (Avelox)

Quinolones are less likely to cause QT prolongation compared with macrolide antibiotics. But the FDA has issued several safety warnings regarding other serious side effects. Your prescriber should consider all these risks before prescribing a quinolone antibiotic.

4. Typical antipsychotics, such as chlorpromazine

Typical antipsychotics treat mental health conditions such as bipolar disorder and schizophrenia. Some also reduce nausea and vomiting.

Typical antipsychotics include medications like:

• Chlorpromazine (Thorazine)

• Haloperidol (Haldol)

• Perphenazine

• Pimozide

• Thioridazine

Of these medications, chlorpromazine and pimozide seem to have the greatest risk for QT prolongation. Keep in mind that most antipsychotics carry a risk of this serious side effect. But in general, typical antipsychotics tend to carry a higher risk for QT prolongation than atypical antipsychotic medications.

5. Atypical antipsychotics, such as ziprasidone

Atypical antipsychotics treat mental health conditions like depression, bipolar disorder, and schizophrenia. They work slightly differently than typical antipsychotics and come with different side effects.

Examples of atypical antipsychotics includes:

• Aripiprazole (Abilify)

• Brexpiprazole (Rexulti)

• Lurasidone (Latuda)

• Olanzapine (Zyprexa)

• Quetiapine (Seroquel)

• Risperidone (Risperdal)

• Ziprasidone (Geodon)

Ziprasidone is associated with a higher risk of QT prolongation compared with other atypical antipsychotics. And some studies have found that lurasidone may have a lower risk compared with others in this group.

6. Tricyclic antidepressants, such as amitriptyline

Tricyclic antidepressants (TCAs) treat depression and other mental health conditions. They’re also frequently prescribed for conditions like nerve pain and migraines.

Examples of common TCAs include:

• Amitriptyline

• Clomipramine (Anafranil)

• Doxepin (Silenor)

• Imipramine

• Nortriptyline (Pamelor)

Most studies show that TCAs can prolong the QT interval, even at low doses.

7. Some selective serotonin reuptake inhibitors, such as citalopram

Other types of antidepressants don’t typically cause QT prolongation. But there are two notable exceptions: citalopram (Celexa) and escitalopram (Lexapro). Both medications belong to a class of antidepressants called selective serotonin reuptake inhibitors (SSRIs).

Citalopram is more likely to cause QT prolongation than escitalopram. And it carries an FDA safety warning related to this side effect. But both medications carry this risk, especially if someone is taking higher-than-recommended doses.

Other medications to be aware of

Most QT-prolonging drugs belong to the groups listed above. But there are others to be aware of that don’t fit into these categories.

These commonly used medications can also prolong the QT interval:

• Fluconazole (Diflucan)

• Hydroxyzine (Vistaril)

• Linezolid (Zyvox)

• Methadone (Methadose)

• Ondansetron (Zofran)

• Sumatriptan (Imitrex)

It’s possible that you may be taking a QT-prolonging drug not listed in this article. It’s a good idea to share an updated medication list with your prescriber and pharmacist. They can tell you if any medications you take have a risk for this side effect.

Should you avoid medications with the risk of QT prolongation?

No, it’s not necessary for most people to avoid QT-prolonging drugs. Remember, it’s a rare side effect. But some people may have a higher risk, such as those who:

• Take more than one medication that prolongs QT

• Take high doses of medications that prolong QT

• Have a history of long QT syndrome

• Have electrolyte problems, such as low potassium or low magnesium

• Have a history of heart problems, including heart disease and heart failure

• Take diuretics (“water pills”)

• Are 65 years or older

The good news is that QT prolongation is not a permanent medication side effect. Your heart rhythm should return to normal once your dose is adjusted or stopped. Always talk to a healthcare professional before changing or stopping any medication.

Why trust our experts?

Written by:

Tegan Smedley, PharmD, APh

Tegan Smedley, PharmD, APh, has 10 years of experience as a pharmacist. She has worked in a variety of settings, including retail, hospital, and ambulatory care.

Reviewed by:

Ferras Bashqoy, PharmD, BCCCP, BCPPS

Ferras Bashqoy, PharmD, BCCCP, BCPPS, is a clinical pharmacotherapy specialist in the Neonatal Intensive Care Unit (NICU) at Hassenfeld Children’s Hospital in New York City. His favorite part of the job is working with preterm newborns because they are strong and mighty despite their size.

Reviewed by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

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