Anticholinergic Toxicity

Overview

Anticholinergic toxicity is a form of poisoning that occurs when the body is exposed to too much of a substance that blocks acetylcholine, a chemical messenger the nervous system uses to control many automatic body functions. Many common medications and some plants have anticholinergic effects, and an overdose, an interaction, or accidental ingestion can produce a recognizable pattern of symptoms.

This pattern, sometimes summarized by clinicians with phrases describing dry, flushed, hot, and confused states, can range from mild to severe. Severe anticholinergic toxicity can cause dangerous agitation, a very high body temperature, abnormal heart rhythms, and seizures, and is a medical emergency. Prompt recognition and treatment, which may include a specific antidote, can be life-saving.

Symptoms

Symptoms reflect the blocking of acetylcholine throughout the body. Common features include:

• Dry mouth and dry skin, with reduced sweating
• Flushed, red skin
• Elevated body temperature
• Dilated (enlarged) pupils and blurred vision
• Fast heart rate
• Confusion, agitation, hallucinations, or restlessness
• Difficulty urinating and a swollen bladder
• Reduced bowel activity

Severe cases can include high fever, severe agitation or delirium, seizures, and dangerous heart rhythm changes. Any suspected overdose or poisoning with these symptoms is a medical emergency. Call poison control or emergency services right away.

Causes

Anticholinergic toxicity is caused by exposure to substances that block acetylcholine. Sources include:

• Antihistamines: Some older allergy and sleep medicines have strong anticholinergic effects, especially in overdose.
• Certain antidepressants and psychiatric medicines: Including some older antidepressants and medications used for various conditions.
• Medicines for bladder, stomach, or movement disorders: Some of these are designed to have anticholinergic effects.
• Plants: Certain plants, such as those in the nightshade family, contain natural anticholinergic compounds.
• Combined effects: Taking several medicines with anticholinergic properties together can add up, particularly in older adults.

Toxicity can result from intentional overdose, accidental ingestion (especially in children), drug interactions, or sensitivity in vulnerable people.

Risk Factors

• Taking high doses of medications with anticholinergic effects
• Using several anticholinergic medicines at the same time
• Older age, with greater sensitivity to these effects
• Accidental ingestion by young children
• Intentional overdose
• Foraging or accidental ingestion of anticholinergic plants

Diagnosis

Diagnosis is based mainly on recognizing the characteristic pattern of symptoms and the history of exposure:

• Clinical assessment: Identifying the combination of dry skin, flushing, fever, dilated pupils, fast heart rate, and confusion.
• History: Information about medications, possible overdose, plant exposure, or access to substances, often gathered from family or caregivers.
• Tests: An ECG to check the heart rhythm, and blood tests to assess overall condition and rule out other causes. Specific drug levels are checked in some situations.

Because many other conditions can cause confusion and fever, clinicians work to distinguish anticholinergic toxicity from other emergencies.

Treatment

Treatment is provided in an emergency setting and focuses on supporting the body and reversing the effects when appropriate:

• Supportive care: Monitoring and supporting breathing, heart rhythm, and blood pressure, and actively cooling the body if the temperature is high.
• Calming agitation: Medications to control severe agitation, delirium, or seizures.
• Limiting absorption: Activated charcoal may be used in certain cases of recent ingestion when appropriate.
• Antidote: In selected cases, a medication called physostigmine may be used under careful monitoring to reverse the toxicity.
• Treating complications: Managing urinary retention, abnormal heart rhythms, and other problems as they arise.

Poison control centers provide expert guidance and should be contacted promptly for any suspected poisoning or overdose.

Prevention

• Take medications only as prescribed and review them with a pharmacist or doctor to avoid combining several anticholinergic drugs
• Store all medications safely and out of reach of children
• Be cautious with over-the-counter sleep aids and allergy medicines, which can have strong anticholinergic effects
• Never eat unknown wild plants or berries
• Keep the poison control number readily available

When to See a Doctor

Anticholinergic toxicity can be a medical emergency. Call poison control or emergency services immediately if someone has taken too much of a medication, ingested an unknown substance or plant, or shows signs such as:

• Confusion, agitation, or hallucinations
• Hot, dry, flushed skin and a high body temperature
• Dilated pupils and a fast heart rate
• Inability to urinate
• Seizures or loss of consciousness

Do not wait to see if symptoms improve. Prompt evaluation and treatment can prevent serious complications, and poison control can advise on the safest next steps.

Related Topics

Frequently Asked Questions

References

1. American Association of Poison Control Centers.
2. MedlinePlus, U.S. National Library of Medicine. Poisoning.
3. Centers for Disease Control and Prevention (CDC). Poisoning prevention.
4. National Capital Poison Center (Poison Control).