What is Anticholinergic Toxicity?
Anticholinergic toxicity, or poisoning from certain drugs, is commonly seen in emergency rooms but is rarely deadly. Data from the 2015 annual report from the American Association of Poison Control Centers shows that there were nearly 14,000 reported cases of exposure to these drugs, but none were fatal. However, in previous years, as many as 51 cases resulted in death. Overdoses can occur accidentally or on purpose. It’s important to understand this because anticholinergic drugs are easily available, and many medications may have side effects related to them. They work by blocking a substance called acetylcholine in the body. A lot of these drugs, and even some plants, contain compounds that can cause this effect.
What Causes Anticholinergic Toxicity?
Anticholinergic substances are widely used, and sometimes misused, across the globe. They can become harmful, typically as a result of an overdose, but even regular use can sometimes lead to mild harmful effects. Most often, these substances are taken orally. Notable naturally occurring anticholinergics include atropine, hyoscyamine, and hyoscine, with atropine serving as a treatment for toxicity from certain poisonous compounds and a quick fix for heart rhythm problems.
Medications that feature anticholinergic properties range from antidepressants, antihistamines, drugs for Parkinson’s disease, antipsychotics, muscle relaxants, and eye-dilating drugs. Some medications have anticholinergic effects as their main action, whereas others exhibit these effects as side effects. It’s particularly risky when multiple anticholinergic drugs are ingested at the same time, a common situation for older adults who are on multiple medications. Overdosing on anticholinergic drugs most commonly involves antihistamines.
Nature, too, provides sources of anticholinergics, particularly amongst plants. Accidental and intentional ingestion is common. Some plants which contain belladonna alkaloids are often misused for their hallucinogenic effects. Additionally, illegal drugs like cocaine and heroin can sometimes be laced with anticholinergics such as hyoscine or atropine. Risk also exists with externally applied forms of these substances.
Risk Factors and Frequency for Anticholinergic Toxicity
In 2015, around 14,000 cases of exposure to anticholinergic, a type of drug, were reported to poison control centers. The next year, over 2 million cases of human exposure to various substances were reported. Out of these, antihistamines, a type of anticholinergic, made up 4.19% of the reported substances. However, these figures may not show the full picture, as many cases aren’t reported to poison control centers.
Signs and Symptoms of Anticholinergic Toxicity
Identifying anticholinergic poisoning is a matter of careful medical history-taking and physical examination. Patients may come in having intentionally swallowed known anticholinergic substances such as antihistamines, or even a plant known as jimson weed. Nevertheless, the details may not always be clear. Some patients might be unable, or unwilling, to disclose what substance they consumed, as in cases of attempted suicide. In other instances, young children may be brought in by a parent or caregiver suspecting they might have swallowed an unknown substance.
Healthcare professionals need to recognize signs and symptoms of anticholinergic poisoning, especially when reliable patient history isn’t available. A helpful mnemonic to remember these symptoms is “red as a beet, dry as a bone, blind as a bat, mad as a hatter, hot as a hare, full as a flask.” Symptoms corresponding to this mnemonic include:
- Flushing or skin redness
- Lack of sweat
- Dry mouth and nose
- Dilated pupils
- Changes in mental state
- Fever
- Difficulty in urination
Additional symptoms can include less active bowel sounds, and effects on the central nervous system that can lead to delirium, hallucinations, restlessness, confusion, unusual speech patterns, and involuntary picking at clothes or bedding. Seizures and uncontrolled body movements may also occur. Some substances, like Diphenhydramine, have been reported to cause abnormalities in the heart rhythm as well.
Testing for Anticholinergic Toxicity
If a doctor suspects that a patient might have been poisoned, they should follow a standard procedure. Just like with any other potentially serious illness, the patient’s breathing, airway and blood circulation should be checked right away. Their vital signs, like temperature, heart rate, breathing rate, blood pressure and oxygen levels, should also be recorded.
The doctor will likely need to expose the patient’s skin to look for things like patches that could be causing toxicity, such as a hyoscine patch. The patient should be continually monitored for heart activity, and an intravenous line (IV) might be set up for easier access to the bloodstream.
Various tests should be completed, including urine tests, urine drug tests, a finger-prick glucose test, tests for salicylate and acetaminophen levels, electrical heart activity test (ECG), and pregnancy test for women. If the patient is having seizures or is running a significant fever, the doctor should carry out further lab tests, including a metabolic panel, liver enzyme checks, and creatine kinase. However, it’s crucial to understand that diagnosis of anticholinergic toxicity (a type of poisoning), is based on clinical symptoms and signs. This condition can be confused with sympathomimetic toxicity, but a lack of sweating indicates anticholinergic toxicity.
Treatment Options for Anticholinergic Toxicity
The main approach to treating anticholinergic toxicity, a type of drug poisoning, is generally supportive care. A key challenge is managing severe restlessness associated with this condition. For this, intravenous benzodiazepines are the preferred treatment. Although large doses may sometimes be necessary, it is crucial to preventing worsening of symptoms like high body temperature and muscle breakdown, known as rhabdomyolysis.
When intravenous benzodiazepines don’t work, Physostigmine, a drug that increases the levels of a neurotransmitter in the brain, may be used in severe cases. In situations of low blood pressure or suspected muscle breakdown, it is crucial to administer intravenous fluids. If high body temperature is detected, cooling the person is important.
The use of activated charcoal can be considered if the patient arrives within one hour of ingestion. This might work even when given a little later, since anticholinergic drugs slow down gut movement. If the patient develops irregular heart rhythm, intravenous sodium bicarbonate should be used.
Physostigmine is typically used when both peripheral (limbs, organs) and central (brain, spinal cord) signs of anticholinergic poisoning are present. Since it works in both these systems, resuscitation equipment should be on standby in case of possible reactions. Doses defer based on if the patient is an adult or a child. A repeat dose may be needed after approximately 30 minutes if symptoms come back. Generally, physostigmine is recommended only for pure anticholinergic poisoning. Intravenous fat emulsion has been reported as a successful treatment for severe cases of an antihistamine overdose that does not respond to other interventions.
Alternatives to Physostigmine are rivastigmine and pyridostigmine. However, rivastigmine only comes in oral and skin patch form, while pyridostigmine comes in an oral and intravenous form. Neither of these options have FDA approval for this use.
What else can Anticholinergic Toxicity be?
A variety of health problems can cause severe confusion, particularly in older individuals. The side effects of various medications, or using many different medications at once, should also be considered as possible causes. Infections of the brain or blood, kidney disease, and certain toxic conditions can all create symptoms that look similar to poisoning from medications that affect the nerve endings in your body. It is also essential to evaluate whether the symptoms are due to solely medication poisoning or if they are mixed, as seen with certain types of antidepressants and antipsychotic medications.
What to expect with Anticholinergic Toxicity
Generally, if anticholinergic toxicity is spotted early and the patient is given the right supportive care, their chances of recovery are pretty good.
Possible Complications When Diagnosed with Anticholinergic Toxicity
Here are some serious complications that can occur:
- Respiratory failure (difficulty in breathing)
- Cardiovascular collapse (sudden failure of the heart)
- Rhabdomyolysis (serious syndrome due to a direct or indirect muscle injury)
- Seizures (sudden, uncontrolled electrical disturbance in the brain)
- Coma (a state of prolonged unconsciousness)
- Permanent disability
- Death
Preventing Anticholinergic Toxicity
People who are on multiple prescriptions need to be aware that side effects associated with anticholinergic medications are common. It’s also crucial that parents and caregivers always store all medicines, both prescription and over-the-counter, in a secure location that children cannot access. It’s also important to remember that you should never take medicine more often than your doctor has instructed and don’t exceed the recommended dose for all kinds of medication, including over-the-counter drugs. Lastly, avoid driving after taking sedating anticholinergics, like antihistamines, as they can make you feel drowsy.
