What Is Antidepressant Toxicity?
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Antidepressant Toxicity - Symptoms, and Treatment

Published on Oct 31, 2022 and last reviewed on Mar 07, 2023   -  5 min read


Antidepressants can cause toxicity if taken in overdose and cause death. To know more about antidepressant toxicity, read the article below.


Antidepressants are those medicines that are used in the treatment of depression. Depression is a mood disorder in which the mental state is altered, and the patient feels sad, hopeless, excessive guilt lacks energy and hope, is unable to sleep, is unable to focus, feels changes in appetite, and sometimes has suicidal thoughts. These antidepressants, in safe doses, can improve the symptoms of depression. However, in excessively higher amounts or lethal doses, it can create toxicity and eventually death of the patient.

What Are the Types of Antidepressants?

Antidepressants are of five types. All these five types are listed below:

  • Tricyclic Antidepressants (TCA): Examples are Amitriptyline and Imipramine.

  • Monoamine Oxidase Inhibitors (MAOIs): Examples are Isocarboxazid and Phenelzine.

  • Selective Serotonin Reuptake Inhibitors (SSRIs): Examples are Duloxetine and Escitalopram.

  • Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): Examples are Duloxetine and Venlafaxine.

  • Atypical Antidepressants: Examples are Bupropion and Vortioxetine.

Among all these types, the toxicity from tricyclic antidepressants is the most common compared to the other antidepressant's toxicity.

What Is Antidepressant Toxicity?

Antidepressant toxicity means the poisoning of antidepressant medicine due to its overdose. In addition, when these medicines are taken in more excessive dosages than required, they show their harmful effects on the body. Antidepressant toxicity poses several health risks and can lead to the patient's death.

What Are the Lethal Doses for Antidepressant Toxicity?

Lethal doses are life-threatening. These are the minimum amount of medicine needed to cause an individual's death. The lethal dosage of an antidepressant depends on the following factors:

1. Tricyclic Antidepressants (TCAs):

TCA toxicity is more prominent than other antidepressants' toxicity, and TCA toxicity has been reported in higher numbers than other antidepressants.

  • Safe Dose: The daily dose of the TCA Amitriptyline, which is considered a safer dose, is between 40 and 100 milligrams (mg). The daily dose of Imipramine, considered safe, is between 75 and 150 mg.

  • Lethal Dose: Doses more than 1000 mg is considered lethal doses, which are life-threatening. However, one study showed that the lowest lethal dose of Imipramine was 200 mg.

2. Selective Serotonin Reuptake Inhibitors (SSRI):

These antidepressants have lower side effects and hence are one of the most prescribed medicines. These are comparatively safe medicines and, if taken alone, are rarely lethal.

  • Safe Dose: The daily dose of SSRI Fluoxetine is between 20 and 80 mg per day.

  • Lethal Dose: The lethal dose of the SSRI Fluoxetine is 520 mg. In addition, the toxicity risk increases when a high dose of SSRI is taken in conjunction with alcohol or other drugs.

3. Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):

The intensity of toxicity of these antidepressants comes in between TCAs and SSRIs. Therefore, these antidepressants are considered less toxic than TCAs. However, they are more harmful than SSRIs.

  • Safe Dose: The daily dose of SNRI Venlafaxine is between 75 and 225 mg.

  • Lethal Dose: A dose of 2,000 mg or 2 g is considered a lethal dose. However, most SNRI overdoses are not lethal. The toxicity of this antidepressant involves its intake in conjunction with other drugs.

4. Monoamine Oxidase Inhibitors (MAOIs):

These antidepressants are not used significantly nowadays. Most overdose cases for this drug occur when overdoses are taken with alcohol or other drugs.

In addition, severe symptoms of lethal dose appear after taking more than 2 mg per kg of body weight. Due to their many interactions with other drugs, these medicines are generally not prescribed. Due to this reason, death from MAOI toxicity is very rare.

What Are the Symptoms of Antidepressant Toxicity?

Symptoms are those features that the patients experience. The symptoms of antidepressant toxicity are listed below:

  • Sweating.

  • Dry mouth.

  • Blurred vision.

  • Drowsiness.

  • Tremors (involuntary shaking of hands or limbs).

  • Confusion.

  • Muscle spasm.

What Are the Signs of Antidepressant Toxicity?

Signs are those features that the doctor notices during a physical examination. The signs of antidepressant toxicity are listed below:

  • Dilated pupils.

  • Rapid pulse.

  • Fast breathing.

  • Rapid heartbeat.

  • Fever.

  • Dry mouth.

  • Warm skin.

  • Altered mental condition.

  • Exaggerated reflexes (hyperreflexia).

  • Agitation (a type of mental state).

  • Decreased bowel sounds.

Signs of Severe Antidepressant Toxicity:

Severe toxicity is a serious condition. The signs of severe antidepressant toxicity are as follows:

  • Coma.

  • Convulsions.

  • Delirium.

  • Respiratory depression (slow and ineffective breathing).

  • Low blood pressure.

  • Abnormal results of the electrocardiogram.

What Is the Treatment of Antidepressant Toxicity?

Treatment of antidepressant toxicity includes the following:

1. For Treating Serotonin Antidepressant Toxicity:

  • Medicine called Benzodiazepine is given for the treatment of agitation and muscular rigidity.

  • Rapid cooling interventions and neuromuscular blocks can manage uncontrolled spasms of muscle and extremely high body temperature.

  • In severe cases, a patient needs to be put under a ventilator.

2. For Treating Tricyclic Antidepressants Toxicity:

  • Activated charcoal can be given soon after a tricyclic antidepressant overdose to reduce the absorption of the medicine.

  • Sodium bicarbonate is provided to help reduce the irregular heartbeat in tricyclic antidepressant toxicity.

  • Lidocaine and beta blockers also manage irregular heartbeat (arrhythmia).

  • Excessively low blood pressure is controlled by norepinephrine.

In addition, patients with tricyclic antidepressant toxicity must be monitored for a minimum of 12 hours afterward. The prognosis of serotonin toxicity is good. Most people can recover completely from serotonin toxicity.

Some cases of serotonin toxicity require neurologist consultation for aftercare. Antidepressant toxicity can be accidental or intentional. In case of intentional toxicity, the patient should be assessed and referred for appropriate treatment to prevent self-harm in the future.

Why Are Antidepressants Used for Self-Poisoning?

Antidepressants are most commonly used to commit suicide by self-poisoning. According to one study, antidepressant self-poisoning accounts for 20 % of all poisoning suicides in the United Kingdom (UK). This result reflects that people who die by suicide often suffer from depression.

The availability of antidepressant medicines to depression patients is also the primary cause of self-poisoning because depression patients always have an abundant amount of prescribed antidepressant medication. In addition, the depressed patient often gets suicidal thoughts.


To conclude, antidepressants are available to help patients suffering from depression. It should be taken in the prescribed doses as suggested by the psychiatrist. In situations where the patient is acutely depressed and having suicidal thoughts, it is recommended that a close family member store the medication safely and give it to the patient daily. This can help to mitigate the risk of taking an impulsive overdose. Overdosing or taking these medicines in excessively high amounts with alcohol or other drugs is life-threatening. Recovery from the overdose is possible if the patient gets medical attention soon after the toxicity.

Frequently Asked Questions


What Is Meant by Antidepressant Toxicity?

Antidepressant toxicity refers to the poisoning resulting from the ingestion of too many antidepressants. In appropriate doses, these antidepressants help lessen the effects of depression. However, in overly high doses or lethal proportions, it can cause toxicity and ultimately result in the patient's death.


How Is Antidepressant Overdose Treated?

The primary goal of antidepressant overdose treatment is to treat its symptoms. For example, in the case of serotonin antidepressant toxicity, symptoms like muscle rigidity and agitation are treated with medication referred to as Benzodiazepines. Uncontrolled muscle spasms and extremely high body temperatures can be controlled with quick cooling interventions and neuromuscular blocks. However, a patient needs to be placed under a ventilator in serious circumstances.
In addition, tricyclic antidepressant toxicity can be treated by administering activated charcoal quickly after a drug overdose to limit its absorption. To deal with the irregular heartbeat caused by tricyclic antidepressant poisoning, sodium bicarbonate is given. Beta-blockers and lidocaine is also used for the same purpose. Norepinephrine regulates abnormally low blood pressure caused by antidepressant toxicity.


What Happens if a Patient Overdoses on Antidepressants?

Antidepressants can manifest their adverse effects on the body when used in amounts that are excessive compared to what is prescribed. Antidepressant toxicity carries a number of health hazards and may even be fatal to the patient.


What Are the Side Effects of Antidepressants?

The side effects of antidepressants are listed below.
- Dry mouth.
- Stomach upset.
- Weight gain. 
- Feeling drowsy or dizzy.
- Blurred vision.
- Either difficulty in sleeping or excessive sleepiness.
- Anxiety or agitation.


What Is the Treatment for Serotonin Syndrome?

People with serotonin syndrome are likely to remain in the hospital for at least 24 hours under intensive observation. The treatment includes the following measures:
Benzodiazepine medications, including Diazepam or Lorazepam, help lessen agitation, seizure symptoms, and tightness of the muscles.
Cyproheptadine, a medication that prevents the synthesis of serotonin.
Intravenous fluids (via veins).
Stopping the drugs that caused the condition.
Additionally, in life-threatening situations, medications that make the muscles still, a temporary breathing tube, and a breathing machine will be required to stop additional muscle injuries.


What Antidepressants Are the Safest?

The three different kinds of antidepressants that are considered safe are listed below.
- Selective serotonin reuptake inhibitors (SSRIs).
- Serotonin and norepinephrine reuptake inhibitors (SNRIs).
- Tricyclic antidepressants (TCAs).


What Is the Rare Side Effect of SSRI Antidepressants?

Serotonin syndrome is a rare adverse effect of SSRIs. When the chemical levels of serotonin in the brain become excessively high, it gives rise to serotonin syndrome. It typically occurs when an SSRI is combined with a medication that also increases serotonin levels, for example some other antidepressant or St. John's wort (a European plant that is used to treat depression).


What Does Serotonin Syndrome Toxicity Mean?

Serotonin toxicity, or serotonin syndrome is a potentially fatal drug-induced illness brought on by an excess of serotonin in the brain's synapses. This life-threatening condition can affect the brain, muscles, and other body parts like the eyes, skin, stomach, etc. In worst case scenario, it can cause seizures, unconsciousness, and even coma.


What Is Meant by a Mild Case of Serotonin Syndrome?

When serotonin, a typical chemical present in excess in the body, serotonin syndrome develops.
It is typically brought on by using substances or medicines that impair serotonin levels. The basic treatment for serotonin syndrome involves stopping the drugs that are responsible. A mild case of serotonin syndrome involves less severe symptoms such as feelings of nervousness, ease of vomiting (nausea), diarrhea, tremors (involuntary shaking of limbs), and dilation of the pupil.


What Is the Most Common Mental Condition Linked With Serotonin?

The most common mental disorder linked with serotonin is depression which is characterized by prolonged periods of sadness. In addition to this, mood disorders can also result if serotonin levels get impaired.


Who Should Refrain From Using Antidepressants?

Individuals with kidney diseases, bleeding disorders, mental disorders like bipolar disorder, and diabetes should not take SSRI antidepressants. Individuals having high blood pressure or other heart diseases should avoid SNRI antidepressants. Individuals with liver diseases, eye diseases like glaucoma, mental disorders like schizophrenia, and an enlarged prostate gland should avoid TCA antidepressants.


Are There Any Long-Term Effects From Antidepressants?

Yes, long-term use of antidepressants may harm the body. The long-term use of SSRIs and TCAs increases the risk of developing type 2 diabetes. It is believed that the weight gain caused by these antidepressants makes the individual more likely to develop type 2 diabetes.


Can Antidepressants Lead To Psychosis?

Yes, antidepressants can lead to psychosis. Studies are underway tp understand why antidepressants sometimes lead to psychosis. According to studies, psychosis may result from the interaction of the sigma receptors with antidepressants. The sigma receptors are scattered throughout the brain and control mood, perception, and cognition.


How Long May an Antidepressant Be Taken?

According to the American Psychiatric Association, if an individual is taking an antidepressant for the first time, they should continue to take it for at least four to five months after the depressive symptoms have subsided. To receive the maximum advantages, this could require taking a prescription for approximately a year. Additionally, the APA advises that one should undergo treatment for a few more years if they have an ongoing major depressive illness or have had three or more depressive episodes. When the risk of relapse is significant, doctors may also recommend an extended course of treatment.

Article Resources

Last reviewed at:
07 Mar 2023  -  5 min read




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