Common Medications That Can Cause Bradycardia

Beta-blockers, certain calcium channel blockers, digoxin, antiarrhythmic drugs, and cholinesterase inhibitors used for dementia are among the most common medications that slow the heart rate enough to cause bradycardia. The good news is that drug-induced bradycardia often resolves once the responsible medication is adjusted or stopped, though not always. Understanding which drugs carry this risk, why some people are more vulnerable than others, and what symptoms warrant a phone call to your doctor can make a real difference in how the problem is caught and handled.

Beta-Blockers

Beta-blockers are prescribed for high blood pressure, heart failure, certain arrhythmias, migraines, and even performance anxiety. They work by blocking the effects of adrenaline on the heart, which lowers heart rate and reduces the force of each beat. That is exactly the therapeutic goal in many cases, but it also means slowing the heart too much is a built-in risk rather than a freak side effect. Drug-induced bradycardia is common during antiarrhythmic therapy, and beta-blockers are considered the major culprits.¹

Common beta-blockers include metoprolol, atenolol, propranolol, carvedilol, and bisoprolol. The risk of excessive heart rate slowing tends to be higher with non-selective beta-blockers like propranolol, which affect the heart and other organs simultaneously, compared to cardio-selective agents like metoprolol. But any beta-blocker can cause bradycardia at high enough doses or in a vulnerable patient. The issue becomes particularly serious when a beta-blocker is combined with another drug that also slows conduction through the heart, such as a non-dihydropyridine calcium channel blocker or digoxin.

Calcium Channel Blockers That Affect Heart Rate

Not all calcium channel blockers carry the same risk. The family splits into two broad groups: dihydropyridines (like amlodipine and nifedipine) and non-dihydropyridines (verapamil and diltiazem). The dihydropyridines mainly relax blood vessels and lower blood pressure without doing much to heart rate. It is the non-dihydropyridines that directly slow the heart’s electrical system.²

Verapamil and diltiazem inhibit the sinoatrial and atrioventricular nodes, which are the parts of the heart responsible for setting its rhythm and relaying electrical signals from the upper chambers to the lower ones. By slowing conduction through these nodes, these drugs can cause sinus bradycardia or even atrioventricular block, where signals between the upper and lower chambers are delayed or dropped entirely.³ The risk climbs when verapamil or diltiazem is taken alongside another agent that slows cardiac conduction, such as a beta-blocker or digoxin.³

If you are on amlodipine or a similar dihydropyridine and wondering whether you should worry about a slow heart rate, the answer is generally no. These drugs are designed to work on blood vessels, not on the heart’s pacemaker cells. The distinction matters because many people hear “calcium channel blocker” and assume the bradycardia warning applies to the whole class.

Antiarrhythmic Drugs and Digoxin

Antiarrhythmic medications are used to control abnormal heart rhythms, which puts them in an awkward position: the same electrical effects that correct one rhythm problem can create another. The American Heart Association has noted that drugs can trigger bradyarrhythmias and other rhythm disturbances, and that drug-induced bradyarrhythmias are significant primarily because of the symptoms they cause.⁴ Amiodarone is perhaps the most well-known offender. It is used for both atrial and ventricular arrhythmias, and its effects on the heart’s electrical system are broad enough that sinus bradycardia and heart block are recognized complications, sometimes appearing weeks or months into treatment because of the drug’s extremely long half-life.

Digoxin, often prescribed for atrial fibrillation and heart failure, slows the heart by increasing the influence of the vagus nerve on the heart’s pacemaker tissue. At therapeutic levels this is useful, but the margin between a helpful dose and a toxic one is notoriously narrow. Older adults and people with kidney problems are especially susceptible to digoxin accumulation because the drug is cleared by the kidneys. Symptoms of digoxin-related bradycardia can include fatigue, dizziness, nausea, and visual changes like seeing halos around lights.

Cholinesterase Inhibitors for Dementia

This category catches many people off guard. Donepezil, rivastigmine, and galantamine are prescribed to manage cognitive symptoms in Alzheimer’s disease and related dementias. They work by boosting levels of acetylcholine, a chemical messenger in the brain involved in memory and learning. The problem is that acetylcholine also acts on the heart. Elevated acetylcholine stimulates cholinergic receptors in cardiac tissue, which increases vagal tone and can slow the heart rate.⁵

The population taking these drugs is almost exclusively older adults, who tend to have reduced ability to compensate for sudden drops in heart rate or blood pressure. That diminished autonomic reserve means that even a modest slowing of the heart can lead to lightheadedness, fainting, or falls.⁵ Falls in elderly patients with dementia are a serious problem on their own, so recognizing a cholinesterase inhibitor as the underlying trigger is genuinely important. It is one of the reasons why heart rate monitoring is recommended when these medications are started or increased.

Why Drug Combinations Are More Dangerous Than Single Drugs

Most cases of serious drug-induced bradycardia involve more than one offending medication. When a beta-blocker and a non-dihydropyridine calcium channel blocker are prescribed together, both are suppressing the heart’s electrical conduction through overlapping pathways. Add digoxin to the mix and you have three drugs simultaneously pushing the heart rate down. Each one alone might produce only mild slowing, but the combined effect can be dramatic.

Severe bradycardia tied to the combination of beta-blocking agents and sodium channel blockers has been documented as a specific clinical concern.¹ This matters for real-world patients because it is common for people with heart conditions to be on several medications at once. A person with atrial fibrillation and high blood pressure might easily end up on a beta-blocker, diltiazem, and digoxin simultaneously, each prescribed for a legitimate reason. The risk is not that any single doctor made a mistake; it is that the cumulative effect on heart rate was not adequately anticipated, especially if prescriptions come from different providers who are not fully aware of each other’s orders.

This is also where over-the-counter and non-cardiac medications can quietly contribute. Eye drops containing timolol, a beta-blocker used for glaucoma, are absorbed systemically and have been implicated in bradycardia. Certain antidepressants and antipsychotics can slow heart rate as well. If you are already on a rate-slowing medication and start something new, even something that seems unrelated to your heart, flagging it with your prescriber is worth the effort.

Who Is Most Vulnerable

Older adults face the highest risk for drug-induced bradycardia, for several reasons that tend to stack. First, aging itself brings changes to the heart’s conduction system. The sinoatrial node loses pacemaker cells over time, and fibrosis can develop in the electrical pathways, making the heart inherently more susceptible to rate-slowing drugs. Second, kidney and liver function decline with age, meaning medications are cleared more slowly and blood levels can creep higher than intended. Third, older adults are far more likely to be taking multiple medications, increasing the odds of problematic combinations.

People with pre-existing conduction disease, even if it has never caused symptoms, are at particular risk. A person whose resting heart rate already sits in the low 50s because of mild underlying conduction delay may tolerate a beta-blocker less well than someone whose baseline is 75. This is why an electrocardiogram before starting rate-slowing medications is standard practice, though it does not always happen in busy clinical settings.

Electrolyte imbalances also make the heart more susceptible. Low potassium, low magnesium, or high potassium can each worsen the conduction-slowing effects of drugs. A patient taking a diuretic that depletes potassium alongside a beta-blocker is in a subtly riskier position than someone on the beta-blocker alone. Thyroid dysfunction matters too: hypothyroidism already slows the heart, and layering a rate-slowing medication on top of unrecognized low thyroid function can produce unexpectedly severe bradycardia.

Symptoms to Watch For

A mildly slow heart rate often produces no symptoms at all. Many athletes have resting rates in the 40s and feel fine. The trouble starts when the slow rate compromises the amount of blood reaching the brain and other organs. Common symptoms include:

Fatigue: persistent tiredness that does not improve with rest, often the earliest and most easily overlooked sign
Dizziness: lightheadedness when standing up or during exertion, sometimes progressing to near-fainting
Syncope: actual fainting episodes, which in older adults can result in injuries from falls
Exercise intolerance: feeling winded or unable to keep up with activities that were previously manageable
Mental fog: difficulty concentrating or a sense of cognitive slowing, sometimes mistaken for progression of dementia in patients already being treated for it

That last point is particularly tricky in patients on cholinesterase inhibitors. If a patient with Alzheimer’s disease starts seeming more confused or begins falling, the natural assumption is that the disease is progressing. In reality, drug-induced bradycardia and its downstream effects on brain perfusion could be the culprit, and recognizing this can prevent unnecessary escalation of dementia treatment while the real problem goes unaddressed.

What Happens When the Drug Is Stopped

In many cases, drug-induced bradycardia resolves once the offending medication is withdrawn or its dose is reduced. A study following patients hospitalized for drug-related bradycardia found that stopping the responsible medication led to resolution of the slow heart rate in about 60% of patients. Among those who recovered and later resumed the same medication, none developed bradycardia again, suggesting that the original episode was related to specific circumstances like dosing, drug interactions, or a temporary change in how the body processed the drug.²

That said, roughly a quarter of patients in the same study had bradycardia that persisted even after the drug was stopped, and most of those individuals ultimately needed a permanent pacemaker.² The interpretation here is that the drug unmasked an underlying conduction problem that was already developing. The medication pushed an aging or borderline electrical system past its tipping point, and removing the drug did not reverse the structural changes that had already occurred. In these cases, the drug was the trigger but not the sole cause.

This distinction matters for how you and your doctor approach the situation. If stopping a medication restores your heart rate to normal, there is a reasonable chance you can eventually return to that drug if it is medically necessary, possibly at a lower dose or with closer monitoring. If the slow rate persists after the drug is gone, further workup is warranted because something beyond the medication is going on.

Medications People Forget to Mention

The drugs discussed so far are the well-known culprits. But several categories of medication fly under the radar when it comes to bradycardia risk. Clonidine, a centrally acting blood pressure medication, reduces sympathetic nervous system activity and can slow the heart substantially, especially if doses are missed and then restarted abruptly. Lithium, used for bipolar disorder, has been associated with sinus node dysfunction, particularly at higher serum levels. Some opioid pain medications can slow the heart, though this tends to be clinically relevant mainly during acute overdose situations.

Ivabradine is worth special mention. Unlike the other drugs on this list, slowing the heart rate is its entire purpose. It selectively blocks the “funny current” in the sinoatrial node and is prescribed for chronic heart failure and certain types of inappropriate fast heart rate. Because it does nothing other than slow the heart, bradycardia is its most predictable side effect. Patients on ivabradine are typically monitored closely, but the risk increases if another rate-slowing agent is added.

Even some non-prescription substances can contribute. Melatonin supplements, though generally safe, have mild heart rate-lowering effects. Cannabis use has been associated with bradycardia in some users. These are unlikely to cause problems on their own, but in someone already on a beta-blocker or diltiazem, they could add just enough rate-slowing effect to tip the balance.

How Drug-Induced Bradycardia Differs from Other Causes

There is a practical reason why identifying a medication as the cause of bradycardia matters more than it might seem. If the slow heart rate is caused by intrinsic disease of the heart’s conduction system, the usual treatment trajectory leads fairly quickly toward a permanent pacemaker. But if a drug is responsible, there is a potential for full resolution without any device. Jumping to a pacemaker without first carefully evaluating whether a medication is the culprit can mean an unnecessary implant, with all the long-term maintenance and small but real risks that come with it.

Clinicians sometimes face a tricky judgment call here. A patient may genuinely need the medication causing the bradycardia, say a beta-blocker after a heart attack, and also genuinely have a slow heart rate that is causing symptoms. In that situation, the decision may be to implant a pacemaker specifically so the patient can continue taking the drug they need. This is not a failure of treatment; it is a deliberate trade-off. But it only makes sense when the alternatives, such as switching to a different medication, reducing the dose, or discontinuing the drug, have been explored and ruled out.

1
PubMed Central. Severe iatrogenic bradycardia related to the combined use of beta-blocking agents and sodium channel blockers
2
Korean Circulation Journal. Prognosis and Natural History of Drug-Related Bradycardia
3
NCBI Bookshelf. Calcium Channel Blockers
4
Circulation. Drug-Induced Arrhythmias: A Scientific Statement From the American Heart Association
5
Elsevier / JAPhA Pharmacotherapy. Risk of bradycardia and syncope associated with the use of cholinesterase inhibitors in patients with Alzheimer disease and related dementias: A systematic review and meta-analysis