What is Tricyclic Antidepressant Toxicity?
Tricyclic antidepressants (TCAs) are a type of medicine that were first used in the late 1950s to treat depression. However, since new kinds of antidepressants, like selective serotonin reuptake inhibitors (SSRIs), came into the picture, the use of TCAs has lessened. Yet, they are still used for treating depression that hasn’t improved with less harsh drugs. In adults, TCAs are also used to prevent migraine headaches, treat nerve-related pain including the pain from Ciguatera poisoning (a type of food poisoning), and to manage obsessive-compulsive disorder. In children, TCAs have been used to treat bed-wetting. Even though TCAs aren’t used as much as before, there has been a rising trend in hospitalizations and deaths related to TCA overdose.
What Causes Tricyclic Antidepressant Toxicity?
Tricyclic Antidepressants (TCAs) are often used to treat people suffering from ongoing pain and mental health conditions. As such, these individuals are more likely to experience toxicity or an overdose – a harmful amount of the drug in the body – simply because they use these drugs regularly to manage their severe health issues. These medications are commonly prescribed, making them easily accessible to these patients.
Risk Factors and Frequency for Tricyclic Antidepressant Toxicity
The data shows that in 1992, there was an overdose rate of TCA (a type of antidepressant) of 1.12 cases per 10,000 people. Recently, more cases of overdose are being found with SSRIs, a different type of antidepressant. However, people who overdose on TCA are more likely to be hospitalized than those who overdose on SSRI. This is because the safe dosage range for TCAs is narrower, making it easier to take too much.
Signs and Symptoms of Tricyclic Antidepressant Toxicity
If a person is suspected to have overdosed on tricyclic antidepressants (TCAs), it’s crucial to seek immediate medical assistance and get an EKG, which is a test that checks heart function. TCAs are powerful drugs, and overloading the system with as little as 10 to 20 mg per kg of body weight can be dangerous. Symptoms usually appear within 30 to 40 minutes, and it’s typically clear within 2 hours if there is toxicity. Some individuals may show signs of toxicity later than this. It’s also crucial to know if the person took any other medications along with the TCAs, particularly pain relievers like acetaminophen or aspirin.
Doctors will closely monitor the patient’s vital signs and perform multiple physical exams to look for signs of specific conditions, referred to as anticholinergic toxidrome, cardiac toxicity, and neurologic toxicity. These examinations play an key role in figuring out how to best treat the patient.
Testing for Tricyclic Antidepressant Toxicity
When a person has been exposed to certain substances, it can affect their heart, nerves, and other body systems. This can lead to changes in their vital signs such as heart rate, body temperature, and blood pressure. In some cases, the person may even struggle to breathe properly or lose the ability to protect their airway.
Fast heart rate is commonly observed due to the impact of the substance on their body. However, more serious issues like irregular or slow heart rates can also occur. Another common symptom is low blood pressure, which can happen due to lack of fluids in the body, the effects of the substance on the heart, or other factors.
Other common symptoms include fever, dilated pupils, dry mouth and skin, decreased bowel sounds (indicating slower movement of food through the digestive system), and changes in mental status. The person may become restless or experience seizures, or they might become less alert and even lose consciousness.
Doctors may start diagnosing these symptoms by first doing an electrocardiogram (EKG). This is a test that records the electrical signals in your heart. This test can help recognize if the substance has affected the sodium and/or potassium channels in the heart, which could lead to heart problems. An EKG can also predict whether seizures or heart rhythm disorders are likely to occur based on certain specific readings.
Along with this, doctors may also suggest basic lab tests and brain scans using computed tomography (CT), if necessary, to rule out other causes for a person’s altered mental status. It is important to note that the level of the substance in the body does not always correlate with the severity of symptoms observed. But it can be helpful in identifying if a specific substance has been ingested when the symptoms point in that direction.
If the person shows any signs of these symptoms, they may need to be admitted to the hospital for at least 24 hours for intensive care. Even those who do not show symptoms immediately should be carefully observed for at least 6 hours for any potential signs of changes in their condition.
Treatment Options for Tricyclic Antidepressant Toxicity
In cases of TCA (tricyclic antidepressants) poisoning, it’s crucial to ensure proper functioning of the airway, breathing, and circulation. If conditions are suitable and the patient’s airway is protected, activated charcoal might be used to help rid the body of the poison. This can be particularly effective if done within two hours of the TCA being swallowed. Doctors also try to avoid letting the body become too acidic because it can worsen the heart and nervous system problems caused by the TCA.
Seizures brought on by the poisoning are typically controlled with a group of medicines called benzodiazepines. If these don’t work, other anti-seizure medicines, such as phenobarbital or propofol, may be used. Sodium bicarbonate (baking soda) is also used in severe cases — such as when the patient is unstable, having seizures, or showing certain changes in their heart rhythm. Sodium bicarbonate can help to correct the heart rhythm and balance the body’s pH levels.
Hypotension, or low blood pressure, can be treated with IV fluids and sodium bicarbonate. If these don’t work, medicines that stimulate the heart, like norepinephrine, might be used. Sodium bicarbonate is also used to treat certain abnormal heart rhythms, and sometimes temporary pacemakers are utilized for serious slow heart rhythms that do not respond to treatment.
Certain treatments need to be avoided, such as flumazenil and certain types of anti-dysrhythmic agents which are medicines intended to correct irregular heartbeats. An Intralipid emulsion, which is essentially a fat emulsion, might be considered for patients who are in critical condition due to an overdose of lipophilic TCA, or TCAs that dissolve in fat.
As TCA bonds strongly with proteins and spread widely within the body, methods like dialysis and hemoperfusion — which are procedures used to remove harmful substances from the blood — are not effective.
What else can Tricyclic Antidepressant Toxicity be?
Sometimes, certain conditions present in similar ways. Here’s a list of conditions that may present themselves similarly:
- Antidepressant toxicity
- Child abuse
- Encephalitis
- Febrile seizures
- Heat exhaustion and heat stroke
- High potassium levels in the blood (Hyperkalemia)
- Low calcium levels in the body (Hypocalcemia)
- Isoniazid toxicity (A reaction to a specific drug used to prevent tuberculosis)
- MDMA toxicity (A reaction to the illegal drug often referred to as Ecstasy or Molly)
- Metabolic acidosis (A condition where there’s too much acid in your body fluids)
Understanding these similarities can help medical professionals spot the correct condition.
