Serotonin Syndrome

Serotonin Syndrome is a rare but potentially serious condition caused by too much serotonin in the body.

It usually occurs when a person takes two or more medications or supplements that increase serotonin levels, but it can also happen from a single medication at a high dose or after a recent dose increase.

Common Causes

Serotonin syndrome can happen when medications that affect serotonin are taken together, such as:

Antidepressants: SSRIs (e.g., fluoxetine, sertraline), SNRIs (e.g., venlafaxine, duloxetine), MAOIs, and tricyclics

Migraine medications: Triptans (e.g., sumatriptan, rizatriptan)

Pain medications: Tramadol, meperidine, fentanyl

Over-the-counter products: Dextromethorphan (found in cough medicines)

Supplements: St. John’s wort, ginseng, tryptophan

Drugs of abuse: MDMA (ecstasy), LSD, cocaine

Always tell your healthcare provider all medications, vitamins, and supplements you are taking to help prevent interactions.

Symptoms to Watch For

Symptoms can appear within hours of taking or increasing a serotonergic medication.

Mild Symptoms:

Restlessness or agitation

Tremor or muscle twitching

Sweating and shivering

Dilated pupils

Rapid heartbeat

Moderate to Severe Symptoms:

High fever

Confusion or hallucinations

Muscle rigidity

Seizures

Irregular heartbeat or dangerously high blood pressure

Loss of consciousness

If you notice these symptoms, seek immediate medical attention—serotonin syndrome can become life-threatening if untreated.

How It’s Diagnosed and Treated

There’s no single test for serotonin syndrome. Diagnosis is based on symptoms, medical history, and recent medication changes.

Treatment usually involves:

Stopping the offending medication(s)

Supportive care: IV fluids, cooling measures, oxygen

Medications: Benzodiazepines for agitation or seizures; sometimes cyproheptadine (a serotonin blocker)

Most people recover within 24–72 hours once treatment begins, especially when recognized early.

Preventing Serotonin Syndrome

You can reduce your risk by:

Avoiding mixing serotonergic medications or supplements without medical guidance

Following prescribed doses carefully

Not stopping or starting psychiatric medications on your own

Consulting your provider before adding herbal or over-the-counter products

If you notice any unusual symptoms after a medication change, call your provider right away.

Key Takeaway

Serotonin syndrome is uncommon but serious. It’s important to know the signs, communicate openly with your healthcare team, and review all your medications regularly.

With awareness and prompt treatment, most people recover fully.

References

Boyer EW, Shannon M. The Serotonin Syndrome. New England Journal of Medicine. 2005;352(11):1112–1120.

Volpi-Abadie J, Kaye AM, Kaye AD. Serotonin Syndrome. The Ochsner Journal. 2013;13(4):533–540.

Foong AL, Grindrod KA, Patel T, Kellar J. Demystifying Serotonin Syndrome (or Serotonin Toxicity). Canadian Family Physician. 2018;64(10):720–727.

National Institute of Mental Health (NIMH). Mental Health Medications. Updated 2024. https://www.nimh.nih.gov/health/topics/mental-health-medications

U.S. Food & Drug Administration (FDA). FDA Drug Safety Communication: Information on Serotonin Syndrome. Updated 2023. https://www.fda.gov/