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Serotonin syndrome: causes, symptoms and treatment

Serotonin syndrome: causes, symptoms and treatment

April 29, 2024

Serotonin (5-HT) is a neurotransmitter produced by the body, and It is necessary for the proper functioning of the organism for various reasons since it is responsible for regulating certain physiological processes. But excess serotonin causes Serotonin syndrome , a set of symptoms of different severity that affects individuals who consume antidepressants.

Its most common cause is overdose or the interaction between drugs that have the ability to increase the release of serotonin.

In this article we explain extensively what functions are responsible for regulating serotonin:

"Serotonin: the 6 effects of this hormone in your body and mind"

The importance of serotonin for the organism

Serotonin is a chemical substance with which neurons communicate, that is, a neurotransmitter . This is synthesized from tryptophan, an essential amino acid provided by diet because it is not manufactured by the body. Some foods that contain tryptophan are: oats, wheat, almonds, eggs or blue fish.


But although many think that serotonin is only found in the brain (acting as a neurotransmitter), the Central Nervous System (CNS) only contains 5% of 5-HT, because the small intestine produces the rest , and serotonin never reaches the brain, but has other functions in the body (for example regulates the state of contraction of the smooth muscles of blood vessels).

Although serotonergic neurons occur in lesser amounts in the brain, their functions in the CNS are very varied, since these neurons are highly branched and carry out a large number of synapses. Some of the most relevant functions of serotonin are: regulate appetite, regulate positive and negative moods, intervene in the filter of sensations (as it relates to concentration), control the level of body temperature, etc.


Serotonin syndrome can be fatal

The excess stimulation of serotonin on postsynaptic receptors 5-HT1A and 5-HT2A at the central and peripheral levels has Negative effects for the organism that they can become very serious and even deadly . The set of symptoms attributed to excessive activity of serotonergic neurotransmission on these receptors is known as serotonin syndrome, and was originally described Oates in 1960.

In recent years the consumption of antidepressants has become very fashionable, and this is the main cause of the increase in cases of this syndrome. Antidepressants that inhibit the reuptake of serotonin are the treatment of choice for depression, anxiety disorders, generalized anxiety, obsessive-compulsive disorder, post-traumatic stress, premenstrual diaphoretic and bulimia nervosa.


The overdose or the combination of these drugs can lead an individual to suffer the serotonin syndrome, and since there are many medications that can cause this condition, the following are the most known pharmacological substances that are associated with serotonin syndrome:

Psychiatric Medications

  • Heterocyclic antidepressants : amitriptyline, imipramine, monoamine oxidase inhibitors (MAOIs)
  • Selective serotonin reuptake inhibitors : citalopram, escitalopram, fluoxetine (prozac), paroxetine, sertraline
  • Selective dopamine and / or norepinephrine reuptake inhibitors : bupropion, duloxetine, venlafaxine
  • Mood stabilizers : carbamazepine, lithium

Neurological drugs

  • Parkinsonian agents : levodopa, amantadine, bromocriptine
  • Opioid agonists : meperidine, fentanyl, hydrocodone, pentazocin
  • Amphetamines : methylphenidate, amphetamines
  • Medications for headache : sumatriptan, eletriptan, rizatriptan
  • Antiemetics : ondansetron, granisetron, metoclopramide
  • Antitussives : dextromethorphan

Other medications

  • Antibiotics : linezolid
  • Drugs of abuse: cocaine, ecstasy, LSD
  • Natural substances : St John's wort, caffeine, l-tryptophan, ginseng
  • Other anesthetics : tramadol

Symptoms of Serotonin Syndrome

Symptoms of serotonin syndrome begin a few hours after overdose or the interaction between drugs that increase the presence of serotonin, and are characterized by what is known as triad: autonomic, neuromuscular and neurological dysfunction. If it is not diagnosed in time and the appropriate measures are taken, Serotoninergic toxicity is associated with high mortality .

The characteristic symptoms are varied and can be mild or severe.Below is the symptomatology that presents an individual with serotonin syndrome:

Treatment of serotonin syndrome

To treat serotonin syndrome properly, it is necessary to have a pharmacological history updated , that includes the medicines or substances of free sale and the fitofármacos.

Mild and moderate cases of serotonergic toxicity can be resolved 24 hours after stopping drug treatment, but much depends on the half-life of the substances involved. Severe cases require immediate hospitalization and intensive care, as the patient may suffer severe hyperthermia, rhabdomyolysis or respiratory failure.

For treatment, even in mild cases, it is usual to administer benzodiazepines to reduce agitation, pseudoconvulsive movements and muscular rigidity. The correct hydration, the control of autonomic instability or the control of fever is usual as a support measure.

Cyproheptadine (Periactin), an H1 antagonist drug with activity on 5-HT2A in smooth muscle and with anticholinergic and antiserotoninergic properties is beneficial, since it manages to reverse the antidepressant effects, and a single dose can block approximately 85 to 95% of the serotonergic receptors.

Bibliographic references:

  • González A. R. (2009). The Serotonin Syndrome Medical Journal of the University of Costa Rica, 3 (3): 16-30
  • Gillman P. Ken. (2006). A review of serotonin toxicity data: implications for the mechanisms of antidepressant drug action. Biol Psychiatry; 59: 1046-1051.

Serotonin Syndrome (April 2024).


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