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Symptoms, Diagnosis, and Management of Beta-Blocker Toxicity

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Beta-blocker toxicity occurs due to accidental or purposeful ingestion of large doses of the drug. Read this article to know more about beta-blocker toxicity.

Written by

Dr. Sameeha M S

Medically reviewed by

Dr. Kaushal Bhavsar

Published At December 13, 2022
Reviewed AtOctober 5, 2023

Introduction

Beta-blockers belong to the class of drugs mainly used for treating high blood pressure, irregular heart rhythms, and recurrent heart attacks. Beta-blockers are used to manage high blood pressure when other medications like diuretics are ineffective for the treatment. These drugs have wide applications due to their effectiveness in managing various cardiac disorders, glaucoma, migraine, hyperthyroidism, and anxiety.

Over the years, beta-blocker overdose and toxicity increased due to widespread use and availability. Beta-blocker toxicity may cause cardiotoxicity and hypotension. Profound cardiotoxicity is observed when a beta-blocker overdose occurs in individuals who have already taken other medications like tricyclic antidepressants and calcium channel blockers. Depending on the beta-blocker involved and underlying health conditions (cardiac diseases), people show different toxicity levels after a drug overdose.

What Are Beta-Blockers?

Beta-blockers are a group of drugs that block the receptor sites for epinephrine, norepinephrine, and catecholamines on adrenergic beta receptors present in the sympathetic nervous system. Beta receptors are mainly found on cells of the smooth muscles, heart muscles, arteries, airways and kidneys, and other tissues that are a part of the sympathetic nervous system. These receptors induce stress responses when they are stimulated by epinephrine. Beta-blockers interfere with the binding of stress hormones and epinephrine to the receptors and reduce the effects of stress hormones.

Beta-blockers that are commonly used for therapeutic purposes are the following.

  • Atenolol.

  • Propranolol.

  • Carvedilol.

  • Metoprolol.

  • Labetalol.

  • Bisoprolol.

  • Nebivolol.

  • Acebutolol.

  • Nadolol.

  • Pindolol.

  • Timolol.

  • Esmolol.

  • Sotalol.

  • Betaxolol.

What Are the Uses of Beta-Blockers?

Beta-blockers are used to treat, improve and prevent various medical conditions.

It includes:

  • Chest pain (angina).

  • High blood pressure.

  • Arrhythmia (irregular heart rhythm).

  • Tremors.

  • Heart attacks.

  • Glaucoma.

  • Hyperthyroidism.

  • Pheochromocytoma.

  • Anxiety disorders.

  • Irregular heartbeat.

  • Mitral valve prolapse.

What Is Beta-Blocker Toxicity?

Beta-blockers are one of the most commonly prescribed medications in the world. As a result, there is an increased chance of drug overdose and abuse, leading to toxic health effects. Beta-blocker toxicity may occur due to accidental ingestion of large doses of the drug or long-term exposure to drug doses more than needed. After ingestion, these drugs are readily absorbed within one to four hours. Toxicity involved with beta-blockers depends on the drug's ability to cross blood-brain barriers.

Highly lipophilic (lipid-soluble) beta-blockers like Propranolol easily cross the blood-brain barrier and induce central nervous system toxicity. In addition, excessive beta-blocker concentration in the body will result in reduced catecholamine (adrenaline) activity and altered stress response. Hypotension, hypoglycemia, bradycardia (heart rate lower than usual), hemodynamic instability, and decreased myocardial contraction are the significant side effects of beta-blocker toxicity.

What Are the Symptoms of Beta-Blocker Toxicity?

Beta-blocker overdose can slow down the heart rate and induce difficulties in breathing. The majority of the patients develop trembling and dizziness after overdose.

The common symptoms associated with beta-blocker overdose are the following.

1. Central Nervous System

  • Weakness.

  • Confusion.

  • Seizures.

  • Excessive sweating.

  • Drowsiness.

  • Nervousness.

  • Altered consciousness.

  • Coma.

2. Cardiovascular System

  • Low blood pressure.

  • Irregular heart rate.

  • Heart failure.

  • Rapid heartbeat.

  • Lightheadedness.

  • Shock.

3. Respiratory System

  • Shortness of breath.

  • Respiratory arrest.

  • Breathing problems.

  • Wheezing (asthmatic patients).

4. Visual System

  • Double vision.

  • Blurred vision.

How Can We Diagnose Beta-Blocker Toxicity?

Beta-blocker overdose mainly involves cardiac and central nervous system toxicity. Prolonged hypotension and bradycardia are the first clinical signs pointing toward an overdose. Beta-blocker overdose can be confirmed based on the patient's drug history and clinical features. Cardiotoxicity related to beta-blockers may cause altered levels of cardiac enzymes in the blood. Myocardial infarction can be ruled out by measuring the cardiac enzyme levels. Serum electrolyte levels can be measured to identify hypokalemia and resultant cardiac arrhythmias. An electrocardiogram (ECG) must be done in patients suspecting beta-blocker toxicity to diagnose and manage cardiac changes that may occur due to toxicity.

How Can We Manage Beta-Blocker Toxicity?

  • Airway Management - Most beta-blockers can cross the blood-brain barrier and induce central nervous system toxicity, which may lead to respiratory arrest. Thus proper airway management must be done in patients with decreased consciousness and respiratory depression. Bronchodilators like Alhuterol and supplemental oxygen therapy can be given to reduce bronchospasm. In the case of deeply obtunded patients, the airway must be managed with a cuffed endotracheal tube.

  • Gastrointestinal Decontamination - This includes charcoal administration, gastric lavage, and total bowel irrigation. Gastric lavage and decontamination are done in patients admitted into the hospital within a few hours (1 to 2 hours) after a fatal overdose. Activated charcoal can be used to reduce drug absorption and limit toxicity. Whole bowel irrigation can be done using polyethylene glycol-release preparation until the rectal effluent is clear.

  • Glucagon - It is considered an essential agent in managing beta-blocker toxicity. Glucagon activates adenylyl cyclase (through a secondary mechanism) and increases cardiac inotropy and thus bypasses beta-blocker receptor blockage. It also helps to overcome hypoglycemia induced by excessive beta-blockers in the body through hepatic gluconeogenesis. An initial dose of 5 to 10 milligrams intravenously is given. Later on, the dosage can be altered based on the patient's response and efficacy.

  • Intravenous Fluids - Fluid resuscitation is essential in managing hypotension and bradycardia induced due to beta-blocker toxicity.

  • Benzodiazepines - They can be given to manage seizures associated with beta-blocker toxicity.

  • Calcium Salts - Decreased intracellular calcium levels may occur due to beta-blocker toxicity. However, it can be somehow managed by giving intravenous calcium.

  • Intralipid Therapy - It is used in cases of severe overdose with highly lipophilic beta-blockers like Propranolol, Nebivolol, and Carvedilol. Intralipid therapy will help to reduce the toxicity of lipophilic drugs by lowering the active drug dose in plasma.

  • High Dose Insulin (Euglycemia) - It helps to increase cardiac contractility and glucose utilization.

Conclusion

Accidental or intentional ingestion of large doses of beta-blockers may cause toxic effects in the body. Neurotoxicity and cardiotoxicity are the dangerous effects induced by beta-blocker overdose. Prolonged hypotension, cardiac arrest, respiratory failure, and altered consciousness are the commonly observed conditions associated with beta-blocker toxicity. Therefore, early diagnosis and efficient medical treatment are essential to prevent hazardous adverse effects such as cardiac arrest and respiratory failure.

Frequently Asked Questions

1.

How to Reverse Beta-Blocker Toxicity?

Beta-blocker toxicity is reversed by treating with calcium salts for hypotensive patients. Atropine, fluids, and glucagon are used with high-dose insulin euglycemia treatment with appropriate monitoring. Isoprenaline is another antidote for propranolol toxicity, which acts by antagonizing bradycardia and hypotension completely.

2.

What Is the Primary Treatment for Beta-Blocker Overdose?

The first line of treatment for beta-blocker overdose where symptomatic bradycardia and hypotension are present is treated with high-dose glucagon infusion that provides inotropic and chronotropic benefits in beta-blocker poisoning.

3.

Which Beta-Blocker Is Considered to Be Most Toxic?

Propranolol (lipid-soluble) is the most toxic beta blocker as it easily crosses the blood-brain barrier and induces CNS (central nervous system) toxicity. Excessive amounts of beta-blockers in the body can reduce adrenaline activity and alter stress response. The side effects of beta-blocker toxicity include hypotension, bradycardia (slow heart rate), hypoglycemia, reduced myocardial contraction, and hemodynamic instability.

4.

How to Diagnose Beta-Blocker Toxicity?

 
Beta-blocker toxicity is diagnosed based on the patient’s drug history and clinical features. The main features of toxicity are cardiac and CNS toxicity and symptoms include hypotension and bradycardia pointing towards beta-blocker overdose. An ECG (electrocardiogram) must be performed to diagnose and manage cardiac changes due to beta-blocker toxicity.

5.

What Is the Treatment for Beta-Blocker Side Effects?

The treatment includes:
- Airway management.
- Gastrointestinal decontamination.
- Glucagon infusion.
- Intravenous fluids.
- Calcium salts
- Benzodiazepines.
- High-dose insulin (euglycemia).
- Intralipid therapy.

6.

What Is the Safe Dosage of Beta-Blocker?

The normal dose of beta-blockers for adults is 80 mg twice a day to treat high blood pressure. The usual dose prescribed depends on the doctor and the individual overall health. If the patient has angina (chest pain) or migraine, the dosage is 40 mg, which can be taken twice or thrice a day. However, one must consult the physician before taking beta-blockers.

7.

Which Are the Three Best and Safest beta-blockers?

Three safe and effective beta blockers are Bisoprolol, Carvedilol, and Metoprolol Succinate, as they are known to be effective in treating tachycardia, hypertension, coronary artery disease, myocardial infarction, congestive heart failure, etc., and have shown lower risk of death due to cardiac failure.

8.

How Does Calcium Act Against Beta-Blocker Overdose?

Treatment with calcium is considered beneficial for beta-blocker overdose or poisoning as it improves the blood pressure and the contractility of the heart. It also improves muscle performance in case of heart failure.

9.

Which Are Three Common Adverse Effects of Beta-Blockers?

Three adverse effects of beta-blockers are:
- Feeling dizzy, tired, or lightheaded.
- Difficulty in sleeping or nightmares.
- Cold Fingers or toes as beta-blockers can affect the blood supply to feet and hands.

10.

Which Is the Effective Beta-Blocker Against Hypertension (BP)?

Beta-blockers are medications used to treat hypertension when other drugs are ineffective. Beta-blockers such as Bisoprolol, metoprolol, Atenolol, etc., are used to treat hypertension, and these drugs act by blocking the effects of epinephrine or adrenaline hormones. They cause the heart to beat slowly, thereby reducing the blood pressure. These drugs also help in improving blood flow.

11.

What Are the Contraindications of Beta-Blockers?

The contraindications of beta-blockers are:
- Peripheral vascular diseases (reduced blood circulation except heart and brain).
- Diabetes mellitus (a metabolic disease characterized by high blood glucose levels).
- Chronic obstructive pulmonary disease (group of diseases that block airflow and cause breathing problems).
- Asthma (inflammation and narrowing of airways that causes wheezing).
 

12.

What Are the Alternatives for Beta-Blockers?

The alternative medications for beta-blockers can be:
- Diuretics: They help in eliminating extra water from the body and can also help in treating high blood pressure
- ACE (Angiotensin-Converting Enzymes) Inhibitors: It lowers blood pressure, relaxes blood vessels, and prevents diabetes-related kidney damage.
Calcium channel blockers.

13.

What Is the Reason to Ban the Use of Beta-Blockers?

Beta-blockers are banned in certain areas like sports because of their anti-tremors and anti-anxiety effects. They also lower the heart rate and can trigger asthma attacks. In diabetic patients, beta-blockers can block signs of hypoglycemia (low blood sugar levels).
Source Article IclonSourcesSource Article Arrow
Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)

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