Serotonin syndrome: what is it?

Serotonin syndrome or serotonin syndrome it is the consequence of very high levels of this neurotransmitter in the central nervous system. Usually this happens due to the interaction between neuropsychiatric drugs.

Serotonin is a substance that participates in numerous brain functions, since it is responsible for regulating mood, attention, sexuality, among others. Are you interested in knowing more about this topic? Next, we tell you more about it. Keep reading!

What causes serotonin syndrome?

When a drug related to the regulation of serotonin levels is consumed in high doses, or when it is combined with another substance with similar activity, the risk of toxicity is greatly increased.

This not only happens in this case, but with most of the drugs available on the market. Toxicity is nothing more than the ability of these substances to produce effects that can be fatal.

A small imbalance in the levels of this important neurotransmitter can have severe consequences. It's more or less the same as seizures or depression.

This last condition is very prevalent throughout the world. If you have some time, the Spanish Society of Psychiatry together with the Royal College of Psychiatrists (United Kingdom) has produced this guide on antidepressant drugs for patients.

Elevated serotonin levels lead to serotonin syndrome. Without treatment, this condition causes serious complications.

Related drugs

The drugs most involved in this syndrome are antidepressants, anti-migraine and cough suppressants. To be more exact, they cover the following:

  • Selective serotonin reuptake inhibitors (SSRIs): They are widely used throughout the world, and act on the neurons of the central nervous system by increasing the amount of serotonin available between them. They include citalopram, sertraline, and fluoxetine.
  • Selective serotonin and norepinephrine reuptake inhibitors (SSRIs): They act in a similar way to the previous group and include drugs such as duloxetine and venlafaxine.
  • Monoamine oxidase inhibitors (MAOIs): were the first antidepressants on the market, and at present they have been displaced by the aforementioned groups. We can mention moclobemide, isocarboxazid and nialamide.
  • Triptans: they are used for acute migraine attacks and tend to cause cerebral vasoconstriction. The most representative example is sumatriptan, but zolmitriptan and rizatriptan are also included.
  • Cough suppressants: Dextromethorphan is used for the symptomatic relief of coughs and can be found in many syrups. Some people use it recreationally by using excessive doses.
  • Illicit drugs: this group includes LSD (capable of inducing hallucinations), cocaine, among others.

To a lesser extent it is possible to find the following medications:

  • Antiparkinsonians: increase the availability of dopamine in the nervous system, such as levodopa.
  • Antiemetics: They serve to reduce nausea and vomiting in a wide variety of disorders. Ondansetron and metoclopramide are some examples.
  • Antibiotics: linezolid is a potent antimicrobial agent that has been associated with serotonin syndrome on some occasions.

Read also: 5 things to remember if you take antidepressants

Symptoms of serotonin syndrome

Serotonin syndrome is a clinical condition with very varied manifestations. Most striking is the presence of involuntary muscle movements that resemble a seizure. The symptoms listed below are the most common:

  • Agitation.
  • Ocular clonus (uncontrolled and disorganized movements of the eyes).
  • Tachycardia (fast heart rate).
  • Diaphoresis (profuse sweating).
  • Diarrhea that cannot be explained for another reason.
  • Hyperthermia (increased body temperature) that can lead to fever.
  • Hyperreflexia (increased intensity of tendon reflexes). This is considered a sign, and is evaluated or induced by the doctor.
  • Hallucinations of any kind, such as visual or auditory.
  • Transient elevation of blood pressure.

Is it always presented the same way?

No. The disease is usually classified based on the intensity and duration of symptoms into three categories: mild, moderate and severe. In general, when symptoms are mild, it is possible to plan an appointment with the doctor, since it does not represent a vital emergency.

In the other two cases, based on the results of the evaluation, hospitalization may be required. In fact, when serotonin syndrome is triggered by the use of modern antidepressant drugs (such as SSRIs), symptoms tend to last longer.

How is it diagnosed?

There are no specific tests to diagnose serotonin syndrome. This is often a diagnosis of exclusion. This means that, due to its infrequency, doctors must rule out more possible causes that explain the symptoms.

Therefore, the diagnosis is clinical. For it, it is necessary to provide detailed information on the consumption of drugs and illicit drugs in the last weeks. The doctor may order blood tests to determine the concentration of these drugs. If it is higher than normal, it could greatly facilitate the diagnostic process.

If necessary, other complementary studies are requested to assess the general condition of the person and plan a treatment. These include a complete blood test, electrocardiogram, computed tomography, among many others.

Computed tomography is one of the complementary treatments in case of suspected serotonin syndrome.

Discover more: 6 foods that help you increase serotonin

Can it be confused with other diseases?

There are several differential diagnoses that clinicians can make when evaluating a patient for these symptoms. The most frequent are summarized below:

  • Anticholinergic syndrome: it is triggered by the consumption of antihistamines, atropine and antidepressants, for example. It also usually causes hypertension, increased heart and respiratory rates.
  • Neuroleptic malignant syndrome: in this case, the neurotransmitter involved is dopamine, and it can be produced by abrupt withdrawal of some medications. In these patients there may be a deterioration of the state of consciousness, later evolving to coma.
  • Malignant hyperthermia: Sometimes when inhaled anesthetics are administered, this syndrome characterized by elevated body temperature, deterioration of muscle tissue (rhabdomyolysis), and extreme rigidity can be triggered.

As you can see, the main difference between these conditions is the drug involved. If you suffer any of the symptoms and need to go to the doctor, keep in mind the recommendations at the end of the article.

Treatment of serotonin syndrome

Therapeutic measures depend to a great extent on the intensity of the symptoms. We will detail it below.

  • Mild cases: It is usually decided to reduce the dose of the drugs indicated above or withdraw some of them.
  • Moderate or severe cases: hospitalization and administration of medications is needed to control the disease.

For the latter case, pharmacological and non-pharmacological measures are usually used. The most commonly used drugs are the following:

  • Cyproheptadine: it is used in some cases due to its potent antiserotonergic activity. This means that it reduces the effects caused by excess serotonin in the brain.
  • Diazepam or lorazepam: used to decrease the intensity of involuntary movements. These belong to the group of benzodiazepines.
  • In some cases, muscle relaxants could also be used and drugs to regulate heart rate.

Non-pharmacological measures include intravenous hydration and oxygen therapy.

Final recommendations

Serotonin or serotonin syndrome is the result of a combination of medications or an excess of just one. Sometimes this cannot be predictable as Each body metabolizes drugs at a different rate.

The most common symptoms include abnormal and involuntary movements, along with nonspecific disturbances such as changes in heart rate, excessive sweating and diarrhea.

The intensity can range from very mild to severe, and in certain cases it is fatal. Therefore, according to medical indication, hospitalization for more intensive treatment is possible.

When to go to the doctor?

If you find yourself consuming some of the medications mentioned in the previous sections together, and you begin to present any of the aforementioned symptoms, schedule an appointment with your treating doctor.

In case the symptoms are too bothersome or of very abrupt appearance, it is better go to the emergency service closest. It is preferable to consult immediately before stopping all medications, as they could generate unwanted adverse effects.

If the symptoms are mild, it is possible to wait until a medical consultation. If they occur abruptly, it is best to go to the emergency room.

How to prepare before going to the doctor?

If possible, put into practice the following recommendations before going to the health center:

  • Write down on a sheet of paper all the medications you are taking. If not possible, be sure to bring them to the appointment. You may find it difficult to remember the names of all of them in the middle of the evaluation.
  • If you have a medical report that describes a condition you have, take it with you.
  • In case of illicit drug use, it is recommended to give the information. Remember that the doctor-patient relationship is confidential.
  • Request the accompaniment of a friend or relative. This is very important if you feel nervous. A close person could supplement the information or better remember what the specialist says.
  • Try to ask for a ride and Do not drive, especially if you are presenting involuntary movements.

What is the specialist who can treat this disease?

In general, the drugs that cause the syndrome are indicated by neurologists and psychiatrists. On some occasions, the family doctor or internist may indicate some varieties. For mild cases, it is advisable to see the doctor who indicated the initial treatment to evaluate a dose adjustment.

In serious situations, patients can be cared for by an interdisciplinary group. This can include internists, emergency physicians, family physicians, neurologists, psychiatrists, and intensivists.