This segment of “In the kNOW” covers serotonin syndrome. What is it? How is it treated? How should it be coded in ICD-10-CM?
We begin with an explanation of what serotonin syndrome is. Serotonin is a chemical that is produced by nerve cells not only in the brain but elsewhere in the body. Serotonin is considered a neurotransmitter. Serotonin syndrome is caused by a drug reaction. This occurs when there is too much serotonin in the body, often as a result of starting a new medication or increasing the dose of a serotonergic medication a patient is already taking. When serotonin is not processed correctly or the body cannot handle processing a serotonin increase, serotonin syndrome can occur.
Symptoms of serotonin syndrome develop quickly, most within 6 hours of administration and usually within 24 hours. The symptoms can vary from mild to life-threatening severity. Mild symptoms can include nervousness, vomiting, and diarrhea. Symptom progression to moderate severity would include muscle spasms, agitation, and abnormal eye movements. Finally, when serotonin syndrome has progressed to the severe stage, symptoms will include abnormal heartbeat, disorientation, and fainting.
Medications that can impact serotonin levels include the following:
- Antidepressants
- Selective serotonin reuptake inhibitors (SSRIs)
- Serotonin-norepinephrine reuptake inhibitors (SNRIs)
- Tricyclic antidepressants
- Monoamine oxidase inhibitors
- Pain medications
- Opioids
- Antibiotics
- Linezolid
- Anti-nausea medications
- Reglan
- Zofran
Additionally, there are dietary and herbal supplements that can contribute to serotonin levels rising such as ginseng, nutmeg, and tryptophan. Various illegal drugs, like LSD and cocaine, can also be culprits.
Treatment for serotonin syndrome will depend on the severity of the symptoms. For mild cases, reducing the dosage or stopping the medication can reverse the symptoms within a few days. For a faster reduction in symptoms, a serotonin blocker, like Periactin, may be given. Those with more moderate symptoms may be kept in the hospital for a day or two to ensure response to treatment. ICU admission is usually required for those with severe serotonin syndrome. IV fluids, oxygen, medications for heart rate, blood pressure, and agitation may be given, with mechanical ventilation needed in extreme cases. When serotonin syndrome is caused by antidepressants, the recovery time will be longer since those medications stay in the body for longer periods of time.
There is not a specific diagnostic test for serotonin syndrome. The patient’s clinical presentation along with history of drugs that are considered serotonergic are the indicators that will point a provider to a diagnosis of serotonin syndrome.
For fiscal year 2025, ICD-10-CM included a new code to capture serotonin syndrome which is G90.81. When a coding professional knows from the documentation what drug is causing the serotonin syndrome, an adverse effect code should also be assigned.
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