Serotonin Toxicity

What is Serotonin Toxicity?

The substance serotonin is one of the neurotransmitters that is found in the body. Although it has several functions, it is primarily known as the mood enhancer. An increased amount of available serotonin in the system causes an imbalance and may produce several signs and symptoms [1, 2].

What is Serotonin?

Just like other neurotransmitters, the nerve cells produce serotonin and they utilize these substances to communicate to each other. Most of the serotonin is found in the digestive system but it is also present in the central nervous system and blood platelets [1, 2]. Serotonin found in the stomach aids in the normal functioning of the gastrointestinal system and control of bowel movements.

Those that are found in the brain helps in the regulation of mood, anxiety, and the sleep-wake cycle. Low amounts of serotonin in the brain are associated with depression. Blood platelets used this chemical to assist in wound healing. Serotonin causes narrowing of tiny arteries which are helpful in clot formation [1]. Serotonin exerts its action through its receptors. Several studies have proven that there are different types of serotonin receptors in the body and they differ in their location, function, and agonists. These receptors play an important role in regulating the amount of available serotonin in the body [3].

Serotonin Levels

The normal range of serotonin in the blood is about 101-283 ng/mL. Elevation of serotonin levels associated with the intake of medications for the management of several conditions. The risk of serotonin toxicity is greatest when 2 medications that affect the level of serotonin is taken at the same time [1, 2, 3, 4, 5].


Antidepressants increase the amount of serotonin by inhibiting the reuptake of serotonin in the receptors. Examples of these medications are citalopram, fluoxetine, and sertraline [1, 2, 3].


Another class of antidepressants known as monoamine oxidase inhibitors increases the available serotonin by preventing the removal of serotonin in the brain. The enzyme known as monoamine oxidase is responsible for removing neurotransmitters such as serotonin, norepinephrine, and dopamine in the brain. By inhibiting the action of the enzyme, these neurotransmitters stay in the brain [1, 2, 3].

Serotonin Antagonist and Reuptake Inhibitor

This another class of antidepressant function by inhibiting the action of serotonin antagonists. One example of this medication is Trazodone. This drug is a treatment of choice for depression because of the absence of the adverse effects associated with other antidepressants [1, 2, 3].

Migraine Medications

Low levels of serotonin are associated with the development of a migraine. Migraine medications such as naratriptan, isocarboxazid, and phenelzine, stimulate the serotonin receptors in the blood vessels to promote vasoconstriction and inhibit pain transmission in the central nervous system [4].

Signs and Symptoms

The signs and symptoms that manifest in patients with serotonin toxicity are related to the increased function of the neurotransmitter. Serotonin toxicity may go unrecognized because of the symptoms, especially in mild cases, are often vague [6].

Neuromuscular symptoms

The most common neuromuscular symptom presented in serotonin toxicity is clonus or muscular spasms with repeated contractions. The patient may also manifest rigidity of the muscles, hyperreflexia or increased muscle reflexes, resting tremor and chattering of the teeth [6].

Mental status alteration

Individuals with mild cases of serotonin toxicity may appear restless and confused. Extremely high levels of serotonin may cause hypomania, agitation, seizures, or coma [6].

Other symptoms

Other findings may include increased bowel movement, increased tone of the peripheral blood vessels, increased coagulation, hyperthermia, tachycardia or increased heart rate, mydriasis or dilation of the pupils and instability of the blood pressure [6].


Mild forms of the toxicity may be resolved within 24-72 hours after stopping the intake of medications but those with more severe forms should be brought to the hospital to receive treatment [2, 5, 6].

Emergency department

The initial priority when the patient arrives is to stabilize the airway, breathing, and circulation. Oxygen support may be given but an intubation may be required especially if the level of consciousness of the patient has been altered. They will be connected to an electrocardiograph machine for an assessment and they may be transferred to the intensive care unit depending on their condition. The serotonin level of the patient will be obtained for assessment and for reference throughout the duration of the treatment [2, 5, 6].

Symptom management

Medications that will be given to the patient will depend on the symptoms that are present. Benzodiazepines such as lorazepam or diazepam will aid in the management of the muscle rigidity, seizures, and agitation. Cardiac medications such as beta-blockers and nitroprusside are given to stabilize the cardiac status of the patient. The drug cyproheptadine is known to inhibit the production of serotonin and it may be given to patients if other treatment modalities are ineffective [2, 5, 6].


In order to prevent the toxicity from happening, drugs that affect the level of serotonin must be taken according to the prescription of the physician. Any medications being taken should be reported before starting any new serotonin-related drugs. Toxicity symptoms must be reported immediately to receive prompt treatment [2, 5, 6].

Those who are taking medications that affect serotonin levels must be aware of the risk of serotonin toxicity. If you have more information about this condition, you can share your thoughts with other readers through the comment section below. Alternatively, you can also share this article on your Facebook or Twitter page to help raise the awareness about serotonin toxicity.


  1. Scaccia, A. (2016, August 22). Serotonin: What You Need to Know. Retrieved from Healthline:
  2. Mayo Clinic Staff. (2015, November 2015). Serotonin syndrome. Retrieved from Mayo Clinic:
  3. EL, S. (2001). Mechanism of migraine and action of antimigraine medications. The Medical Clinics of North America, 943-958.
  4. Upadhyay, S. (2003). Serotonin Receptors, Agonists and Antagonists. Indian Journal of Nuclear Medicine, 1-11.
  5. Goldberg, J. (2014, November 18). What Is Serotonin Syndrome? Retrieved from WebMD:
  6. Cushing, T. A. (2016, September 8). Selective Serotonin Reuptake Inhibitor Toxicity. Retrieved from Medscape:

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