The medicines most likely to slow your heart are the ones prescribed to work on the heart or blood pressure, because slowing the heart is often part of what they are meant to do. But a slow pulse can also come from drugs taken for something else entirely, from memory problems to mood disorders to glaucoma eye drops.1Internal Medicine. Bradycardia Shock Caused by the Combined Use of Carteolol Eye Drops and Verapamil in an Elderly Patient with Atrial Fibrillation and Chronic Kidney Disease The good news is that drug-related slowing is often reversible, since the heart rate usually recovers once the medicine is adjusted.2PubMed Central. Drug-induced bradycardia
How Slow Is Too Slow and How Medicines Do It
Doctors call a resting heart rate below 60 beats per minute bradycardia, which simply means a slow heart rate. Plenty of healthy people, especially fit ones and people who are asleep, sit in the 50s with no trouble at all. So a slow reading matters mostly when it comes with symptoms or keeps dropping.
If a smartwatch or blood pressure cuff flags a slow pulse, check it by hand, since wrist devices can undercount when beats are weak or irregular: count for 30 seconds and double it. One low reading at rest or during sleep is less concerning than repeated low readings during the day. Note the time, what you were doing, and any symptoms, so you have something to show your doctor.
The heartbeat starts in a small natural pacemaker in the upper heart, and the signal then passes through a relay point to the lower chambers. Some drugs slow that pacemaker itself. Others delay or block the signal at the relay, which doctors call heart block.3PubMed Central. Junctional Bradycardia as Early Sign of Digoxin Toxicity in a Premature Infant with Congestive Heart Failure due to a Left to Right Shunt Many drugs get there another way, by damping the body’s “speed up” nerve signals, the adrenaline system.4PubMed Central. Dexmedetomidine attenuates the positive chronotropic effects of intravenous atropine in patients with bradycardia during spinal anaesthesia: a retrospective study
Heart block is different from a simply slow pulse. Some beats never reach the pumping chambers, so the pulse can feel skipped or very slow, and pauses of several seconds can bring on fainting. It usually takes an ECG to identify, not just a pulse count.
A rate that keeps drifting lower over days or weeks after starting a medicine matters more than one low number. Symptoms are covered below.
Heart and Blood Pressure Medicines
Beta-blockers are the most familiar cause. Drugs such as metoprolol, atenolol, bisoprolol and carvedilol slow the heart by blocking adrenaline’s effect on it.5PubMed. Pharmacologic differences between beta blockers That makes a slow heart rate, heart block, and low blood pressure their main side effects.6PubMed. Evaluation of β-Blocker-Induced Bradyarrhythmia Using an Analysis of the Japanese Adverse Drug Event Report Database Nearly every beta-blocker studied has been linked to slow heart rhythms, and severe cases have led to stopping the drug or needing a pacemaker.7PubMed. Evaluation of β-Blocker-Induced Bradyarrhythmia Using an Analysis of the Japanese Adverse Drug Event Report Database The exception is pindolol, which slightly stimulates the heart at rest, so it tends to slow the pulse less than the others.8PubMed. Pharmacologic differences between beta blockers
Beta-blockers are easy to miss on a medicine list. Most names end in -olol or -alol, like propranolol or labetalol. Propranolol is also prescribed for anxiety, migraine and tremor, so people may not think of it as a heart drug. Combination pills can also hide a beta-blocker behind a single brand name.
The different beta-blockers are not interchangeable when it comes to pulse. They vary in how strongly they slow the heart, so a switch from one to another can sometimes change the pulse noticeably. Because the choice is made with your heart condition in mind, don’t switch between beta-blockers or cut the dose on your own.
Calcium channel blockers are often described as one family, so a person told they take one may assume the whole class behaves the same way. It doesn’t. Verapamil and diltiazem slow the signal through the heart’s relay point.9PubMed. Comparative effects of three calcium antagonists, diltiazem, verapamil and nifedipine, on the sinoatrial and atrioventricular nodes. Experimental and clinical studies Nifedipine and similar drugs (amlodipine-type) mainly relax blood vessels and lower blood pressure in a way that makes the body speed the heart back up, so they rarely slow it in practice.10PubMed. Comparative effects of three calcium antagonists, diltiazem, verapamil and nifedipine, on the sinoatrial and atrioventricular nodes. Experimental and clinical studies If you’re unsure which one you take, ask the pharmacist.
Digoxin is more complicated. At normal doses it does not appear to raise the risk of rhythm problems.11PubMed Central. Junctional Bradycardia as Early Sign of Digoxin Toxicity in a Premature Infant with Congestive Heart Failure due to a Left to Right Shunt When levels in the blood climb too high, though, it can cause a very slow heart and heart block, often alongside nausea and confusion.12PubMed Central. Junctional Bradycardia as Early Sign of Digoxin Toxicity in a Premature Infant with Congestive Heart Failure due to a Left to Right Shunt Loss of appetite and vomiting are common early clues, and some people see yellow-green halos. Kidney problems or dehydration can push levels up without any change in dose. A blood test of the digoxin level helps, though doctors read it alongside symptoms and other blood tests.
Slow rhythms are also the most common rhythm side effect of drugs used to control irregular heartbeats, such as amiodarone, sotalol and flecainide.13Cardiovascular Prevention and Pharmacotherapy. Adverse reactions to antiarrhythmic drugs And ivabradine, a newer drug for heart failure and angina, slows the pacemaker directly and can cause a slow heart rate with or without symptoms.14Oregon State University Drug Use Research & Management Program. New Drug Evaluation: ivabradine tablet, oral
Medicines Outside Cardiology That Slow the Heart
The common Alzheimer’s drugs donepezil, rivastigmine and galantamine boost a nerve chemical that helps memory but also acts on the heart’s pacemaker, which responds by slowing down. Recently starting one of these roughly doubled the chance of being hospitalized for a slow heart rate.15PubMed Central. Cholinesterase Inhibitors and Hospitalization for Bradycardia: A Population-Based Study On donepezil, the higher 10 mg dose slowed the heart more than 5 mg.16PubMed. Donepezil decreases heart rate in elderly patients with Alzheimer’s disease The risk is higher when the person is also taking a beta-blocker or another heart-slowing drug.
For an older relative, a slow heart can be mistaken for the dementia itself or for aging. A new fall or faint after starting a dementia drug deserves a pulse check. Caregivers can count the pulse at the wrist and write it down daily for a week, and the prescriber should hear about the timing of any faint or fall after a recent start or dose increase.
Lithium for bipolar disorder can affect the heart’s pacemaker, and a slow regular pulse is its most common heart effect, making up about two-thirds of reported cases.17PubMed. Lithium-associated bradycardia: A systematic review of 121 case reports Beta-blocker eye drops for glaucoma, such as timolol or carteolol, get absorbed into the body and can slow the heart like a pill.18Internal Medicine. Bradycardia Shock Caused by the Combined Use of Carteolol Eye Drops and Verapamil in an Elderly Patient with Atrial Fibrillation and Chronic Kidney Disease In one older patient, carteolol drops combined with verapamil led to a dangerously slow heart and shock.19Internal Medicine. Bradycardia Shock Caused by the Combined Use of Carteolol Eye Drops and Verapamil in an Elderly Patient with Atrial Fibrillation and Chronic Kidney Disease
You can reduce how much of an eye drop gets absorbed. Close the eye rather than blinking hard, and press gently on the inner corner of the eye for about two minutes after each drop. Tell every doctor about eye drops too, since they are often left off medication lists.
Several other drugs belong on the list. The sedative dexmedetomidine, used in hospitals, lowers heart rate and blood pressure.20PubMed Central. Dexmedetomidine attenuates the positive chronotropic effects of intravenous atropine in patients with bradycardia during spinal anaesthesia: a retrospective study Fentanyl-type opioids can slow the heart sharply during anesthesia.21PubMed. Adverse effects of opioid agonists and agonist-antagonists in anaesthesia The lung cancer drug crizotinib can slow the heart’s pacemaker.22PubMed Central. Bradyarrhythmias Associated with Oncologic Treatment—An Updated Review In one reported case, the bowel drug mesalamine slowed the heart to about 40 within a day, and it recovered within a day of stopping.23PubMed Central. Drug-induced bradycardia Supplements such as black cohosh are only occasionally reported to slow the heart, with little firm evidence.24PubMed Central. Black Cohosh: An Uncommon Culprit of Bradycardia in Postmenopausal Women
When It Starts and Who Is Most at Risk
Slow rhythms from beta-blockers usually show up within the first 2 months of treatment.25PubMed. Evaluation of β-Blocker-Induced Bradyarrhythmia Using an Analysis of the Japanese Adverse Drug Event Report Database The first weeks after starting or increasing a dose are therefore when to watch most closely. After the first couple of months, new slowing is less typical, though a new drug or illness can restart the clock.
Two drugs that each slow the heart add up, as with a beta-blocker plus verapamil or diltiazem.26PubMed Central. Adverse effects using combined rate-slowing antihypertensive agents Rhythm drugs that act on sodium channels can likewise strengthen the slowing of beta-blockers.27PubMed Central. Severe iatrogenic bradycardia related to the combined use of beta-blocking agents and sodium channel blockers Prescribers sometimes use both kinds on purpose, with monitoring, so the point is awareness and checking rather than never combining. Different specialists may each add a slowing drug without knowing about the other, so a pharmacist review of all your medicines helps catch overlaps.
Age and other health conditions raise the risk too. Older adults are more prone to heart block or slow rhythms from rhythm drugs, beta-blockers and calcium blockers.28PubMed Central. Use of antiarrhythmic drugs in elderly patients A past heart attack is another known risk.29Cardiovascular Prevention and Pharmacotherapy. Adverse reactions to antiarrhythmic drugs Kidney disease and many medicines at once make harmful interactions more likely.30Internal Medicine. Bradycardia Shock Caused by the Combined Use of Carteolol Eye Drops and Verapamil in an Elderly Patient with Atrial Fibrillation and Chronic Kidney Disease
Babies born to mothers taking beta-blockers such as labetalol late in pregnancy have a higher chance of slow heart rate and low blood sugar after birth.31PubMed Central. Late Pregnancy β Blocker Exposure and Risks of Neonatal Hypoglycemia and Bradycardia If that’s you, the baby’s heart rate and blood sugar are often checked after birth, and these effects are usually short-lived and managed in the nursery. Don’t stop the medicine on your own, since high blood pressure in pregnancy carries its own risks.
Symptoms That Mean You Should Act
Signs include dizziness, unusual tiredness, breathlessness on exertion, or confusion. Chest discomfort and giddiness were the first complaints in the mesalamine case.32PubMed Central. Drug-induced bradycardia Symptoms that appear soon after a new medicine or dose increase point more strongly toward the drug. Those that come with exertion, like getting winded climbing stairs, are easy to blame on age or fitness.
Many drug-related slow rhythms are mild, but heart block and certain rhythm effects can be dangerous.33Circulation. Drug-Induced Arrhythmias: A Scientific Statement From the American Heart Association Fainting, chest pain, severe shortness of breath or a pulse in the 30s needs emergency care. Do not stop a heart medicine abruptly on your own, since stopping beta-blockers suddenly can trigger chest pain or a fast heart.
How urgently to act depends on the picture. Mild tiredness with a pulse in the 50s calls for a call to the prescriber that week. Dizziness, near-fainting or a pulse below 45 with symptoms warrants a same-day call or urgent care. Fainting, chest pain or confusion means calling emergency services. Bring the medicine bottles or a list either way.
How Doctors Confirm the Cause and Treat It
Expect questions about every medicine, an exam, an ECG, and blood tests for other fixable causes like thyroid or potassium problems.34Tamil Nadu Journal of Pharmaceutical Research. Symptomatic Bradycardia Associated with Beta-Blocker Therapy: Clinical Recognition, Risk Factors, Management and Pharmacovigilance-A Narrative Review An ECG records the heart’s electrical signals and can show whether the pacemaker is slow or the relay is delayed. It can show heart block, which a pulse count alone cannot tell apart from a simple slowing. If symptoms come and go, a doctor may arrange a wearable monitor that records over days to catch an episode.
If the heart rate improves after the drug is lowered or stopped, that supports the drug being the cause.35Tamil Nadu Journal of Pharmaceutical Research. Symptomatic Bradycardia Associated with Beta-Blocker Therapy: Clinical Recognition, Risk Factors, Management and Pharmacovigilance-A Narrative Review To make the visit count, bring all prescriptions, eye drops, supplements and over-the-counter products, your logged pulse readings, and when symptoms happened. Add when each medicine was started or changed, plus any recent illness, vomiting or kidney test results.
Often the fix is a lower dose, a switch, or stopping one of two overlapping drugs. Doctors usually avoid restarting a drug that caused a dangerous slowdown just to test it.36Tamil Nadu Journal of Pharmaceutical Research. Symptomatic Bradycardia Associated with Beta-Blocker Therapy: Clinical Recognition, Risk Factors, Management and Pharmacovigilance-A Narrative Review If the medicine is still needed, it may be restarted carefully with monitoring.37Tamil Nadu Journal of Pharmaceutical Research. Symptomatic Bradycardia Associated with Beta-Blocker Therapy: Clinical Recognition, Risk Factors, Management and Pharmacovigilance-A Narrative Review In emergencies, IV glucagon has helped people on beta-blockers or calcium blockers whose heart didn’t respond to standard medicine.38PubMed. A potential role for glucagon in the treatment of drug-induced symptomatic bradycardia
A pacemaker is sometimes needed when the drug can’t be stopped.39PubMed. Evaluation of β-Blocker-Induced Bradyarrhythmia Using an Analysis of the Japanese Adverse Drug Event Report Database Some people need a beta-blocker or rhythm drug for heart failure or atrial fibrillation, and a pacemaker sets a minimum heart rate so the drug can continue. The decision is usually made by a heart rhythm specialist.
Lowering Your Risk When You Take These Medicines
Check your resting pulse before starting one of these drugs so you know your baseline. Then recheck it several times a week during the first 2 months, at rest at about the same time of day, and write down the number, the date, and any symptoms.
Ask your pharmacist whether any new medicine also slows the heart before adding it. If you take digoxin, keep scheduled blood tests, especially when ill or dehydrated.
Mention herbal products and supplements to your prescriber, since they may interact with heart drugs, even though solid evidence about them is thin and some sites list many. Don’t add a supplement to offset a heart medicine without your doctor’s say-so.
It’s also worth asking whether a slow pulse at night is expected on your medicine, and whether changing the timing of your dose could reduce daytime dizziness. If symptoms bother you, report them rather than skipping doses.