Conditions · Emergency medicine and toxicology
Beta-blocker and calcium-channel-blocker overdose !
Poisoning by heart and blood-pressure medicines that slow the heart and weaken its pumping, leading to very low pulse, low blood pressure and shock.
Updated 2026-11-01
Structures involved
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Why it happens
- Shock: types, stages and the organs it damages
- The SA node pacemaker potential
- Cardiac excitation–contraction coupling
- G protein-coupled receptors and cAMP
What it is
Toxicity from an excess of beta-adrenergic blockers or calcium-channel blockers, two classes widely used for hypertension, angina and rhythm control. Both produce bradycardia, conduction block and hypotension; they are taught together because their recognition and rescue therapies overlap, while a few features (blood glucose, mental status) help tell them apart.
Who gets it
Cardiovascular drugs are among the medicines most often involved in fatal poisonings, and calcium-channel blockers cause a large share of those deaths. Because these drugs are cheap, common and often kept at home for older relatives, overdoses occur both as self-harm in adults and as accidental ingestion by toddlers, in whom a single adult tablet of a sustained-release product can be dangerous.
Causes
- Intentional ingestion (self-harm), often with other drugs or alcohol
- Accidental ingestion by young children of a relative's tablets
- Therapeutic errors: dose duplication, drug interactions or reduced clearance in liver or kidney disease
- Calcium-channel blockers: non-dihydropyridines (verapamil, diltiazem) act mainly on the heart; dihydropyridines (amlodipine, nifedipine) mainly dilate arteries
- Beta-blockers: lipophilic or membrane-stabilising agents (propranolol) and sotalol carry extra risks
Risk factors
- Depression, previous self-harm and access to a relative's heart medicines
- Sustained-release preparations, which give delayed and prolonged toxicity
- Co-ingestion of other cardiac drugs (digoxin, antiarrhythmics) or sedatives
- Older age, heart failure and pre-existing conduction disease
- Young children in homes where these drugs are not stored safely
Pathophysiology
Beta-blockade lowers cyclic AMP in cardiac cells, slowing the sinoatrial node, delaying atrioventricular conduction and reducing contractility. Calcium-channel blockers block L-type channels in the nodes, myocardium and vascular smooth muscle, causing bradycardia, heart block, weak contraction and vasodilation. They also block calcium-dependent insulin release from the pancreas, so calcium-channel blocker overdose characteristically raises blood glucose, while beta-blocker overdose can lower it, especially in children. Propranolol blocks sodium channels (wide QRS, seizures) and sotalol prolongs the QT interval.
Classification
- Beta-blocker overdose versus calcium-channel blocker overdose
- Calcium-channel blockers: non-dihydropyridine (cardiac depression, bradycardia) and dihydropyridine (vasodilation with reflex tachycardia early on)
- Immediate-release versus sustained-release ingestion
Symptoms and signs
- Slow pulse, dizziness, fainting and weakness
- Low blood pressure, cool skin and reduced urine output
- Fatigue, drowsiness, confusion and, in severe cases, seizures or coma
- Shortness of breath from heart failure or bronchospasm (beta-blockers in people with asthma)
- Nausea and vomiting
- Calcium-channel blockers: mental status is often preserved until late despite marked hypotension
Diagnosis
- Clinical
- History of the drug, formulation, amount and time, plus bradycardia and hypotension. Blood glucose helps: hyperglycaemia suggests a calcium-channel blocker, hypoglycaemia a beta-blocker. Continuous cardiac monitoring is started at once.
- Tests
- 12-lead ECG (heart rate, PR interval, QRS width, QT), capillary and serum glucose, electrolytes including potassium and calcium, kidney function, lactate and blood gas, and paracetamol and salicylate levels to exclude co-ingestions. Specific drug levels are not useful for acute management.
- Imaging
- Chest X-ray if pulmonary oedema or aspiration is suspected; bedside echocardiography to judge contractility and guide vasopressor choice.
Differential diagnosis
- Digoxin toxicity
- Clonidine or other central alpha-2 agonist poisoning
- Organophosphate or carbamate poisoning
- Hyperkalaemia, hypothyroidism or hypothermia causing bradycardia
- Acute myocardial infarction with heart block
- Sepsis with bradycardia or other causes of shock
Goal of treatment
Restore perfusion of the brain, heart and kidneys by supporting heart rate, contractility and vascular tone, prevent further absorption, and monitor closely for delayed effects of sustained-release drugs.
Treatment
- Acute
- ABC approach with airway protection, intravenous access, fluid boluses and continuous ECG, blood-pressure and glucose monitoring; atropine for symptomatic bradycardia, although it often has limited effect.
- Medical
- Gastrointestinal decontamination with activated charcoal in an alert, early-presenting patient; whole-bowel irrigation may be considered for large sustained-release ingestions, decided by a toxicologist.
- Medical
- Rescue therapies: intravenous calcium salts, high-dose insulin with glucose (insulin-euglycaemia therapy) to improve contractility, glucagon (especially for beta-blockers), and vasopressors or inotropes such as noradrenaline or adrenaline; sodium bicarbonate for wide QRS from propranolol; intravenous lipid emulsion in refractory cases.
- Procedure
- Transcutaneous or transvenous pacing for refractory bradycardia, and extracorporeal life support (ECMO) in specialised centres when shock does not respond.
- Follow-up
- Intensive care admission; hourly vital signs, frequent glucose and potassium checks during insulin therapy, urine output and mental status, with prolonged observation after sustained-release ingestions. Psychiatric evaluation after recovery from intentional overdose.
Complications
- Cardiogenic and vasodilatory shock
- Complete heart block, asystole and cardiac arrest
- Acute kidney injury and mesenteric ischaemia from low perfusion
- Non-cardiogenic pulmonary oedema (calcium-channel blockers)
- Seizures and coma (propranolol)
- Hypoglycaemia or hypokalaemia during insulin-euglycaemia therapy
Prognosis
Most people with mild toxicity recover within a day with supportive care. Large ingestions of verapamil, diltiazem or propranolol, delayed presentation and refractory shock carry the highest mortality, but survival is good when aggressive support and, if needed, extracorporeal support are started early.
Prevention
- Safe storage of medicines out of children's reach and in original containers
- Screening for suicide risk in people prescribed these drugs and limiting quantities dispensed when risk is high
- Medication reconciliation to avoid duplicated or interacting prescriptions in older adults
Test yourself
Think of the answer, then tap the question to see it.
Which laboratory finding helps distinguish calcium-channel blocker from beta-blocker overdose?
Blood glucose: calcium-channel blockers cause hyperglycaemia (blocked insulin release), while beta-blockers tend to cause hypoglycaemia, mainly in children.
Why are sustained-release ingestions observed for a prolonged period?
Toxicity can be delayed by many hours, so a patient who looks well early may deteriorate later.
Which therapy improves contractility in calcium-channel blocker overdose by helping the myocardium use glucose?
High-dose insulin with glucose (insulin-euglycaemia therapy), with close glucose and potassium monitoring.
Which antidote acts on its own receptor to raise cyclic AMP and is classically used in beta-blocker overdose?
Glucagon, which bypasses the beta receptor to increase heart rate and contractility; vomiting is a frequent side effect.
Which beta-blocker causes wide QRS and seizures because it blocks sodium channels?
Propranolol, a lipophilic membrane-stabilising beta-blocker; wide QRS is treated with sodium bicarbonate.
Related conditions
- Digoxin toxicity
- Atrioventricular (heart) block
- Cardiogenic shock
- Cardiac arrest (VF, pulseless VT, asystole, PEA)
- Hypoglycaemia (including insulin-induced)
- Tricyclic antidepressant overdose
- Lactic acidosis
- Suicidal behaviour and suicide risk
- Acute kidney injury
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Beta-blockers overdose (MedlinePlus, US National Library of Medicine, 2026); Calcium-channel blocker overdose (MedlinePlus, US National Library of Medicine, 2026).
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