Drug-induced arrhythmias are a serious and sometimes life-threatening cardiovascular side effect of many commonly used medications. These abnormal heart rhythms can range from bradycardia (slow heart rate) to ventricular tachycardia, atrial fibrillation, or even torsades de pointes—a specific type of polymorphic ventricular tachycardia associated with QT prolongation and a risk of sudden cardiac death.
In this article, we’ll examine the key causes, risk factors, and drug classes associated with drug-induced cardiac arrhythmias, based on current evidence from cardiology and pharmacology literature.
Table of Contents
What Causes Drug-Induced Arrhythmias?
At their core, drug-induced arrhythmias are caused by medications that disrupt the heart’s electrophysiology, particularly its ion channels and receptors. These drugs can interfere with:
- Sodium, potassium, or calcium channels
- Autonomic regulation of the heart rate
- Repolarization of cardiac cells
This disruption affects the heart’s ability to conduct electrical impulses, resulting in abnormal rhythms seen on an ECG (electrocardiogram).
Common Drug Classes That Can Cause Arrhythmias
1. Antiarrhythmic Drugs (Paradoxical Risk)
Some drugs intended to treat arrhythmias can ironically cause them, especially in vulnerable patients.
- Amiodarone
- Sotalol
- Flecainide
- Propafenone
These may lead to QT interval prolongation or bradyarrhythmias, especially in patients with underlying heart disease.
2. Antipsychotics and Antidepressants
These drugs can prolong the QTc interval and are linked to torsades de pointes and other ventricular arrhythmias.
- Haloperidol
- Ziprasidone
- Amitriptyline
- Citalopram
Use caution in elderly patients or those with electrolyte imbalances or heart failure.
3. Macrolide Antibiotics (e.g., Azithromycin)
The FDA and American Heart Association have issued warnings about azithromycin, especially when combined with other QT-prolonging drugs.
- Also includes: Erythromycin, Clarithromycin
- Chloroquine and hydroxychloroquine can prolong QT and cause polymorphic ventricular tachycardia, particularly in COVID-19 treatment contexts.
5. Stimulants
Used in ADHD or weight loss, stimulants like amphetamine, methylphenidate, and even pseudoephedrine may trigger tachycardia, supraventricular tachycardia, or worsen atrial fibrillation in predisposed individuals.
6. Inotropic Agents and Digoxin
- Digoxin can cause bradyarrhythmias or ventricular arrhythmias, especially with toxicity.
- Inotropic drugs (like dopamine or dobutamine) can provoke tachyarrhythmias in unstable patients.
Key Risk Factors for Drug-Induced Arrhythmias
The Tisdale Risk Score, developed at the University of Arizona’s School of Medicine, is widely used to predict the risk of drug-induced QT prolongation in hospitalized patients.
Common Risk Factors Include:
- Prolonged baseline QT interval
- Electrolyte abnormalities (low magnesium, potassium, or calcium)
- Heart failure or structural heart disease
- Bradycardia
- Female sex
- Drug interactions (especially involving CYP450 inhibitors)
- High doses or rapid IV administration
- Older age
- Multiple QT-prolonging drugs combined
How Are These Detected?
Most drug-induced arrhythmias are detected via:
- Electrocardiogram (ECG or EKG)
- Monitoring of QTc interval
- Evaluation of heart rate variability
Treatment and Prevention
Discontinuation:
The first step is often to discontinue the offending drug. In many cases, the QT interval returns to normal after drug withdrawal.
Electrolyte Correction:
Replenishing magnesium and potassium can reduce arrhythmia risk.
Pharmacological Intervention:
In severe cases like torsades de pointes, magnesium sulfate IV is the treatment of choice. Beta-blockers may help stabilize heart rhythm in other arrhythmias.
Cardiology Referral:
Persistent or high-risk arrhythmias should prompt cardiology or electrophysiology consultation.
Final Thoughts
Drug-induced arrhythmias can be triggered by a wide range of medications, including antipsychotics, antibiotics, antiarrhythmics, stimulants, and cardiac drugs. The risk increases with QT prolongation, electrolyte imbalances, and pre-existing heart disease.
Understanding the side effects, pharmacology, and proper electrocardiographic monitoring of these drugs is essential to protect patients from sudden cardiac death and serious heart rhythm disorders.
When in doubt, always consult a healthcare professional—especially when combining medications or treating patients with known cardiovascular dysfunction.
Published on: 2025-06-30
Updated on: 2025-06-30
