Health Library

Calcium-channel blocker overdose

Calcium-channel blockers are a type of medicine used to treat high blood pressure and heart rhythm disturbances. They are one of several classes of medicines used to treat the heart and related conditions. These medicines are a common cause of poisoning.

Calcium-channel blocker overdose occurs when someone takes more than the normal or recommended amount of this medicine.

This article is for information only. DO NOT use it to treat or manage an actual overdose. If you or someone you are with has an overdose, call the local emergency number (such as 911), or the local poison control center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States.

I Would Like to Learn About:

Poisonous Ingredient

The specific ingredients in each type of calcium-channel blocker vary. However, the main ingredient is called a calcium-channel antagonist. It relaxes your blood vessels which lowers your blood pressure and also may affect the contractions of your heart.

Where Found

Calcium-channel blockers are found in these medicines:

• Amlodipine
• Diltiazem
• Felodipine
• Isradipine
• Nicardipine
• Nifedipine
• Nimodipine
• Verapamil

Other medicines may also contain calcium-channel blockers.

Symptoms

Symptoms of a calcium-channel blocker overdose include:

• Agitation (hyperactivity) and delirium (confused thinking and possible hallucinations)
• Breathing difficulty
• Confusion
• Constipation
• Lightheadedness, dizziness
• Drowsiness
• Increased blood sugar
• Irregular heartbeat
• Nausea and vomiting
• Rapid heartbeat
• Slow heartbeat
• Slurred speech
• Shock (extremely low blood pressure)
• Weakness

Home Care

Seek medical help right away. Do NOT make a person throw up unless poison control or a health care provider tells you to do so.

Before Calling Emergency

Have this information ready:

• Person's age, weight, and condition
• Name of the medicine (strength, if known)
• Time it was swallowed
• Amount swallowed

Poison Control

The local poison control center can be reached directly by calling the national toll-free Poison Help hotline (1800-222-1222) from anywhere in the United States. This national hotline will let you talk to experts in poisoning. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

You can also get online poison help now at Poisonhelp.org. Just enter the product, poison, or medicine to get expert help.

What to Expect at the Emergency Room

If you go to the emergency room, take the container for the medicine with you, if possible.

The provider will measure and monitor the person's vital signs, including temperature, pulse, breathing rate, and blood pressure.

Tests that may be done include:

• Blood and urine tests
• Chest x-ray
• Electrocardiogram (ECG), or heart tracing

Treatment may include:

• Activated charcoal
• Breathing support, which may include oxygen or a ventilator (tube through the mouth into the lungs and breathing machine)
• Intravenous fluids (IV, given through a vein)
• Laxatives
• Medicine to treat symptoms and reverse the effect of the drug
• Pacemaker for the heart for serious heart rhythm disturbances

Outlook (Prognosis)

Taking too much of a calcium-channel blocker can be very dangerous. Death can occur, especially with verapamil. If the person's heart rate and blood pressure can be corrected, survival is likely. Survival depends on how much and what type of this medicine the person took and how quickly they receive treatment.

An overnight hospital stay may be required even in less serious cases, as some long-acting medicines preparations remain in the body for many hours.

Risk factors for a more severe outcome, including multiple organ failure and death, include:

• Co-ingestion with other medicines which affect the heart; for example, digoxin, calcium channel blockers, tricyclic antidepressants
• People with other health conditions, such as congestive heart failure and heart rhythm disturbances

Verapamil (a type of calcium channel blocker) overdose is associated with the highest mortality risk.

References

Aronson JK. Calcium channel blockers. In: Aronson JK, ed. Meyler's Side Effects of Drugs. 16th ed. Waltham, MA: Elsevier; 2016:23-39.

Cole JB. Cardiovascular drugs. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 142.

Meehan TJ. Care of the poisoned patient. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts  and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 135.

Review Date: 7/1/2025  

Reviewed By: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

A.D.A.M., Inc. is accredited by URAC, for Health Content Provider (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics. This site complies with the HONcode standard for trustworthy health information: verify here.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language.

© 1997- 2026 A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

All content on this site including text, images, graphics, audio, video, data, metadata, and compilations is protected by copyright and other intellectual property laws. You may view the content for personal, noncommercial use. Any other use requires prior written consent from Ebix. You may not copy, reproduce, distribute, transmit, display, publish, reverse-engineer, adapt, modify, store beyond ordinary browser caching, index, mine, scrape, or create derivative works from this content. You may not use automated tools to access or extract content, including to create embeddings, vectors, datasets, or indexes for retrieval systems. Use of any content for training, fine-tuning, calibrating, testing, evaluating, or improving AI systems of any kind is prohibited without express written consent. This includes large language models, machine learning models, neural networks, generative systems, retrieval-augmented systems, and any software that ingests content to produce outputs. Any unauthorized use of the content including AI-related use is a violation of our rights and may result in legal action, damages, and statutory penalties to the fullest extent permitted by law. Ebix reserves the right to enforce its rights through legal, technological, and contractual measures.