Serotonin syndrome is the accumulation of too much serotonin in your body, resulting in a series of various signs. When an individual takes a combination of medications that contain serotonin (commonly prescribed antidepressants such as Zoloft, Lexapro, both SSRIS and Effexor, an SNRI), they are at a high risk for developing serotonin syndrome.

On occasion, taking one medication to increase serotonin levels can also result in serotonin syndrome in susceptible individuals. Before starting any medication, it is vital that you discuss all the medications you are taking with your doctor to avoid this potentially lethal condition.

What is Serotonin?

Serotonin is a chemical produced by the body that helps to regulate mood, social behavior, sexual desire, sleep, and appetite. As a neurotransmitter, serotonin carries signals between nerve cells. It is produced in the intestines and the brain, but is also present in the central nervous system (CNS) and blood platelets. As a result, serotonin is believed to influence a wide range of psychological and bodily functions.

What Does Serotonin Syndrome Feel Like?

If you start taking a serotonin-related medication, increase your dosage, or begin another in combination with one you are already taking and too much serotonin accumulates, you will feel the effects within several hours. Symptoms can range from mild to severe and depend on the level of serotonin in your body. At best, the signs and symptoms of serotonin are unpleasant; at worst, they can be extremely worrying and require intensive medical treatment.

Serotonin Syndrome Symptoms

The following symptoms are signs that you are experiencing serotonin syndrome:

  • Headaches
  • Shivering
  • Goosebumps
  • Heavy sweating
  • Restlessness
  • Agitation
  • Dilated pupils
  • Confusion
  • Diarrhea
  • Rapid heart rate
  • High blood pressure
  • Muscle rigidity
  • Loss of muscle coordination
  • Twitching muscles

If you experience these symptoms, contact your doctor as soon as possible to discuss the best course of action. However, severe serotonin syndrome can be life-threatening and if you experience any of the symptoms below you should seek emergency treatment immediately:

  • Irregular heartbeat
  • High fever (>103 F/40 C)
  • Seizures
  • Unconsciousness

How Long Does Serotonin Syndrome Last?

How long serotonin syndrome lasts is dependent on how high serotonin levels are in the body. In cases where serotonin syndrome is only present in a mild form, symptoms may be alleviated within 24 hours of discontinuing the medication causing the uptake in serotonin. However, some antidepressants can cause symptoms to last longer as serotonin levels may take weeks to return to normal.

How Common is Serotonin Syndrome?

According to the American Association of Poison Control Centers Toxic Exposure Surveillance System 8,187 people were diagnosed as having serotonin toxicity due to selective serotonin reuptake inhibitors (SSRIs) in 2004. Of these cases, 103 deaths occurred. However, given that statistics on serotonin syndrome are limited, it is likely much more common than the data indicates as those that suffer from mild to moderate serotonin toxicity often go undiagnosed or unreported.

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Serotonin syndrome most often occurs when you combine two serotonin-related medications, though, in some cases, taking one drug that increases serotonin levels may induce the condition in some individuals.

For example, serotonin syndrome could occur if you combine an antidepressant medication with an opioid medication.

Which Medications Cause Serotonin Syndrome?

Drugs and supplements that could lead to serotonin syndrome if taken together or in high doses include:

  • Selective serotonin reuptake inhibitors (SSRIs): antidepressants such as citalopram (Celexa), fluoxetine (Prozac), paroxetine (Paxil) and sertraline (Zoloft)
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs), antidepressants such as trazodone, duloxetine (Cymbalta) and venlafaxine (Effexor)
  • Tricyclic antidepressants, such as amitriptyline and nortriptyline (Pamelor)
  • Anti-migraine medications
  • Pain medications: opioid medications including codeine (Tylenol with codeine), fentanyl (Duragesic), hydrocodone meperidine (Demerol), oxycodone (Oxycontin, Percocet, Percodan) and tramadol (Ultram).
  • Lithium
  • Street drugs: LSD, cocaine, ecstasy, and amphetamines
  • Anti-nausea medications
  • Cough and cold medications
  • Herbal supplements: St. John’s wort, ginseng, and nutmeg
  • Cannabinoids may also influence serotonin

Is Serotonin Syndrome Fatal?

If medical treatment is not sought when serotonin levels get too high, severe serotonin syndrome can lead to unconsciousness and death. Intentional serotonin overdose using anti-depressant medications is one instance in which serotonin syndrome is likely to be fatal without prompt medical treatment.

Can Serotonin Syndrome Be Reversed?

The symptoms of serotonin syndrome usually subside once you stop taking the medication causing the symptoms. Fortunately, there are generally no long-term or lasting complications of serotonin syndrome, though you should be conscious to avoid serotonin syndrome in the future. Talk to your doctor about prevention, especially if you are taking multiple medications that contain serotonin.

Serotonin Syndrome Treatment

Depending on where serotonin syndrome symptoms fall on a scale of mild to severe, treatment will vary in complexity. Typically, doctors will instruct the patient to stop taking the medication causing the elevated serotonin levels as the first course of action. Medications will not disappear from the body immediately and patients will be carefully monitored for any adverse reactions or withdrawal symptoms.

  • “Some patients with high body temperature or hyperthermia will need external cooling measures, similar to those used when treating someone with heat stroke,” Kyle Moylan, MD, FACP told ACP Hospitalist. “In cases where a patient’s blood pressure is very high or very low, short-acting agents should be used because changes in blood pressure can occur very quickly.” An IV and Cyproheptadine (Periactin), a drug that blocks serotonin production, may also be needed.

Finally, in some cases, benzodiazepines may also be given if the patient has severe symptoms and needs to be sedated.

Overall, it’s important to stay informed about your medications. Knowing what you are taking, the active ingredients, possible side effects, and medications that should not be mixed are important in avoiding serotonin syndrome. Pay close attention to the instructions of your medications to ensure you are taking them at correct intervals. If you have questions about your medications, reach out to your doctor to double check that you are not mixing medications that could result in serotonin syndrome.

While you should not be scared if you’ve been assigned one of the medications listed above that contains serotonin, it is vital to keep aware of the effects that mixed medications can have on one another.

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Last Updated: Mar 19, 2019