What Medications Cause a Low Heart Rate?

Dozens of medications can slow your heart rate below the normal resting range of 60 beats per minute, a condition called bradycardia. Beta-blockers are the single most common offenders, but the list extends well beyond them into calcium channel blockers, drugs for dementia, medications for multiple sclerosis, and even some herbal preparations. Whether a slow heart rate actually causes problems depends on how low it drops, how quickly the change happens, and what other medications or conditions are in the mix.

Beta-Blockers Are the Most Frequent Cause

If you take a beta-blocker and your heart rate has dipped, you are far from alone. In a study screening over 2,300 hospital admissions among older adults, beta-blockers were the most commonly prescribed rate-slowing drug found in patients admitted with bradycardia, with bisoprolol alone accounting for the majority of those prescriptions.¹ That study also found that sinus bradycardia, the simplest form of slow heart rhythm, was the most common rhythm disturbance in those patients.

Beta-blockers work by dampening the effects of adrenaline on the heart. That is precisely why they are prescribed for high blood pressure, heart failure, and certain arrhythmias: a slower heart uses less oxygen and pumps more efficiently in many disease states. Common examples include metoprolol, atenolol, propranolol, carvedilol, and bisoprolol. The heart-rate-lowering effect is not a side effect so much as a built-in feature, which means the line between “working as intended” and “too much of a good thing” can be thin. The risk goes up at higher doses, in older adults, and when kidney function declines (since some beta-blockers are cleared by the kidneys).

Non-Dihydropyridine Calcium Channel Blockers

Calcium channel blockers are a broad drug class, but only certain members slow heart rate meaningfully. The ones to watch are verapamil and diltiazem, sometimes called the “non-dihydropyridine” types. These drugs affect the electrical conduction through the heart’s atrioventricular (AV) node, the gateway between the upper and lower chambers. Verapamil and diltiazem both slow AV nodal conduction, though verapamil tends to have a greater effect on the node’s recovery time.² Diltiazem, meanwhile, has more of a tendency to reduce the actual heart rate.³

Nifedipine and amlodipine, the other common calcium channel blockers, belong to the dihydropyridine family and mostly relax blood vessels rather than slow the heart. They rarely cause bradycardia on their own at standard doses. This is a practical distinction worth knowing: if your doctor switches you from diltiazem to amlodipine, a slower heart rate is less likely with the new drug, even though both belong to the same broad class.

Other Heart Medications That Slow the Pulse

Several drugs prescribed specifically for heart rhythm problems can themselves push the rate too low. The American Heart Association has noted that drug-induced bradyarrhythmias are a recognized complication of antiarrhythmic therapy, and while they are mainly a problem because of the symptoms they cause, in some cases they can lead to serious consequences.⁴ Amiodarone, flecainide, and sotalol are common examples. Sotalol is worth special mention because it doubles as a beta-blocker, so its heart-rate-lowering effect comes from two mechanisms at once.

Digoxin, one of the oldest heart drugs still in use, slows the heart by increasing the tone of the vagus nerve, which acts as the body’s natural brake on heart rate. It has a narrow therapeutic window, meaning the difference between an effective dose and a toxic dose is small. Even modest changes in kidney function can push digoxin levels into the danger zone, and one of the earliest signs of toxicity is an excessively slow pulse.

Ivabradine is a newer drug that works by a completely different mechanism. It targets a specific ion channel in the heart’s natural pacemaker cells, selectively slowing the rate without affecting blood pressure or heart muscle contractility.⁵ It has been studied in thousands of patients with stable angina.⁶ Because its entire purpose is to make the heart beat slower, bradycardia is the most predictable adverse effect, especially at higher doses or in people who already have a low resting heart rate.

Non-Cardiac Drugs That Can Slow Your Heart

Some of the most overlooked causes of drug-induced bradycardia are medications prescribed for conditions that have nothing to do with the heart. This is where people get caught off guard.

Cholinesterase inhibitors, used to manage Alzheimer’s disease, are a good example. Donepezil, the most widely prescribed drug in this class, increases a neurotransmitter called acetylcholine throughout the body, including in the heart, where acetylcholine acts as a natural brake on heart rate. A study in elderly patients found that higher-dose donepezil (10 mg) produced significantly slower heart rates and longer conduction intervals compared to the lower 5 mg dose, with a clear dose-dependent relationship.⁷ This matters because the patients taking these drugs are often elderly, may already be on beta-blockers for blood pressure or heart disease, and may not be monitored closely for cardiac effects.

Fingolimod, used to treat relapsing multiple sclerosis, causes a temporary but sometimes dramatic drop in heart rate after the very first dose. Pooled data from three large trials found that the approved dose reduced heart rate by about 8 beats per minute, peaking around four to five hours after the first pill.⁸ Symptomatic bradycardia occurred in a small fraction of patients and typically resolved on its own, but AV conduction delays were also observed. Because of this first-dose effect, patients are typically monitored in a clinic for at least six hours after their initial dose.

Clonidine and dexmedetomidine, which lower blood pressure and provide sedation by acting on receptors in the brain, both reduce heart rate as a core part of their pharmacology. In a study of critically ill cardiac surgery patients, heart rate dropped by a median of 10 beats per minute in both groups, and around 6 to 8 percent of patients developed clinically meaningful bradycardia.⁹

Other non-cardiac medications that have been linked to bradycardia include lithium (used for bipolar disorder), phenytoin (a seizure medication), tricyclic antidepressants, and even mesalamine, a drug used for inflammatory bowel disease.⁴ These are rarer causes, but they illustrate that bradycardia can crop up in places you would not expect.

The Real Danger Is Stacking Drugs Together

Individual medications slow the heart through their own pathways, but the risk jumps sharply when two or more rate-slowing drugs are combined. A patient on a beta-blocker and a non-dihydropyridine calcium channel blocker at the same time, for instance, is hitting the AV node with two different brakes simultaneously. Case reports describe exactly this scenario leading to a dangerous cascade known as BRASH syndrome: bradycardia, renal failure, AV blockade, shock, and hyperkalemia. In one reported case, the synergy between these drug classes alone was enough to trigger the syndrome, requiring a temporary pacemaker before the patient recovered.¹⁰

The vicious cycle works like this: the combined drug effect slows the heart, which drops blood pressure, which reduces blood flow to the kidneys. As the kidneys fail, they stop clearing potassium efficiently. Rising potassium levels further suppress the heart’s electrical activity, pushing the rate even lower. One published case documented a patient on metoprolol, amlodipine, clonidine, and enalapril together whose heart rate fell into the 30s and did not respond to standard rescue medications.¹¹ The takeaway for patients is straightforward: if you are prescribed multiple medications that can each slow your heart, especially if you have any degree of kidney impairment, your doctor should be monitoring your heart rate and kidney function carefully.

Herbal Supplements Are Not Automatically Safe

People sometimes assume that herbal and “natural” products cannot cause the same cardiac problems as prescription drugs, but that assumption has sent people to the emergency room. Aconite root, known as Fuzi in traditional Chinese medicine, contains alkaloids with potent effects on the heart’s sodium channels. A case report documented a patient who developed sinus bradycardia and low-amplitude heart signals within an hour of consuming an aconite root decoction she had prepared herself.¹² Aconite is one of the more dramatic examples, but other botanical products with cardiac-slowing potential include lily of the valley (which contains cardiac glycosides similar to digoxin) and certain forms of hawthorn extract. Because supplements are not regulated with the same rigor as prescription medications, doses are inconsistent and interactions with prescribed drugs are poorly studied.

Why Some People Are More Vulnerable

Age is the single biggest risk multiplier for drug-induced bradycardia. Older adults metabolize drugs more slowly, are more likely to be on multiple medications, and are more likely to have pre-existing conduction system disease that lowers their baseline heart rate before any drug is added. The hospital study cited earlier focused specifically on adults over 70, reflecting the clinical reality that drug-induced bradycardia severe enough to require hospitalization overwhelmingly affects older patients.¹

Kidney impairment magnifies the problem because many heart-rate-lowering drugs (or their active metabolites) are cleared by the kidneys. When kidney function drops, drug levels climb, and the heart sees a bigger dose than intended. This is a major reason why the BRASH syndrome cases described above tend to involve renal failure as a central feature of the spiral.

Genetics can also play a role, though this is still a developing area of medicine. Certain liver enzymes that break down calcium channel blockers vary in activity from person to person based on genetic differences. A case report described a patient who developed severe bradycardia from nimodipine, a calcium channel blocker given after a brain hemorrhage. Genetic testing revealed she had a genotype associated with poor metabolism of the drug, which likely caused drug levels to build up far beyond what was intended.¹³ Pharmacogenomic testing is not routine for most of these drugs yet, but it is a plausible explanation for why some patients develop severe bradycardia on doses that are well tolerated by most.

How to Recognize It

Mild bradycardia from medication often produces no symptoms at all. Plenty of people on beta-blockers walk around with a resting heart rate in the 50s and feel perfectly fine. The problems start when the rate drops low enough to reduce blood flow to the brain and organs. Typical symptoms include dizziness or lightheadedness, fatigue that seems disproportionate to your activity level, feeling faint or actually fainting, shortness of breath on mild exertion, and mental fogginess or confusion.

On an electrocardiogram, drug-induced bradycardia can show up as simple slowing of the sinus rhythm, but it can also produce more concerning patterns. A study of 38 patients with drug-related bradycardia found that about a third had sinus bradycardia with junctional escape beats (a backup rhythm from deeper in the heart), and nearly a fifth had complete third-degree AV block. Third-degree AV block, wider QRS complexes, and rates low enough to need a temporary pacemaker were the markers that signaled the most serious cases.¹⁴

If you are checking your own heart rate at home, using a pulse oximeter or a smartwatch, keep in mind that a single low reading does not mean much. Readings during sleep or deep relaxation are naturally lower. The concerning pattern is a sustained resting heart rate below 50, or below 60 with new symptoms like the ones described above, especially if you recently started a new medication or had a dose increase.

What Happens When It Gets Serious

The first step in managing drug-induced bradycardia is almost always the simplest: stop or reduce the offending medication. In many cases, the heart rate normalizes within hours to a day or two once the drug clears the system. But when the bradycardia is severe, with heart rates in the 30s or 40s and dropping blood pressure, the situation becomes an emergency.

Atropine, the classic first-line drug for bradycardia, blocks the vagus nerve’s slowing effect on the heart. It works reasonably well for mild cases, but it has been inconsistent in reversing severe drug-induced bradycardia, particularly from beta-blocker overdose. Glucagon has emerged as an important alternative in those situations. It increases heart rate and contractility through a pathway that bypasses the blocked beta-receptors entirely, which is exactly why it works when atropine does not.¹⁵ Clinical experience has confirmed that glucagon can resolve symptomatic bradycardia and low blood pressure in patients on maintenance beta-blocker therapy, sometimes making additional treatments unnecessary.¹⁶

In cases involving combined beta-blocker and calcium channel blocker toxicity, where cardiovascular collapse can be resistant to standard vasopressors, high-dose insulin infusion and lipid emulsion therapy have shown benefit. One published case documented significant hemodynamic improvement after these therapies were added when conventional treatments had failed.¹⁷ Temporary pacemakers are the backstop when nothing else restores an adequate heart rate.

When Stopping the Medication Is the Right Call

Not every episode of drug-induced bradycardia means you need to stop your medication permanently. A slow heart rate without symptoms, especially in someone who is physically fit, may require nothing more than monitoring and possibly a dose adjustment. But the calculation shifts as people age, accumulate more prescriptions, or develop new health conditions that change how drugs are metabolized.

Deprescribing, the deliberate and structured process of stopping medications that are no longer providing net benefit, has become an increasingly important concept in cardiovascular medicine. Reasonable triggers include present or anticipated adverse drug reactions, unnecessary accumulation of multiple medications, and the need to match drug regimens to realistic goals of care as life expectancy or functional status changes.¹⁸ For someone who was started on a beta-blocker ten years ago for mild hypertension and now has a resting heart rate of 48 with occasional dizziness, the original reason for the prescription may no longer justify the risk. That conversation with a doctor is worth having, especially because abruptly stopping beta-blockers or clonidine can itself cause dangerous rebound effects. Tapering under medical supervision, rather than quitting cold turkey, is the safe approach.

If you are on any combination of the drugs discussed here and you notice your heart rate running consistently lower than usual, the most productive step is to bring it up at your next appointment with a specific question: given my current medications and kidney function, is my heart rate where you would expect it to be? That framing gives your doctor something concrete to evaluate rather than a vague complaint, and it opens the door to a dose reduction or medication swap before the slow rate becomes a problem that lands you in the emergency department.