Serotonin Syndrome Symptoms, Causes and Treatments

Serotonin Syndrome is a potentially life-threatening adverse drug reaction to high levels of Serotonin in the body. Serotonin is a neurotransmitter, which means it transmit messages throughout the nervous system.

Using medications that stimulate the production of Serotonin in the body, or medications that slow its removal from the body, can cause Serotonin toxicity in susceptible individuals. Developing Serotonin Syndrome after taking just one drug is possible, but the condition occurs most often when the consumer combines two or more Serotonin-concentration altering medications.

An individual may develop Serotonin toxicity after accidentally combining an antidepressant with migraine medication, for example. Serotonin Syndrome may also be the result of intentional overdose of antidepressant medications.

Signs of Serotonin Syndrome can include confusion, dizziness, irritability, vomiting and nausea. In serious cases, more dangerous symptoms may be experienced. If you think you may be experiencing serotonin toxicity, seek out medical attention immediately for the appropriate treatment.

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Serotonin Function Overview

Serotonin, also known as 5-Hydroxytryptamine (5-HT), attaches to specific 5-HT receptors located on various cells throughout the body. Once it binds to the receptor, Serotonin initiates a set of reactions within the cell.

Serotonin causes different actions, depending on the type of receptor it binds to. Most famously, this neurotransmitter is known for promoting happy and relaxed states of mind when released in the brain. But Serotonin also acts as a hormone in other parts of the body, where it can have various physiological effects.

Once bound to a blood vessel cell, for example, Serotonin will cause the blood vessel to narrow and constrict. In the gut, Serotonin plays a role in processes related to digestion.

Under normal circumstances, nerve cells in the central nervous system produce Serotonin to regulate functions such as mood, sleep, attention, behavior, and body temperature. Other nerve cells in the body, particularly those in the intestines, produce serotonin to help regulate the digestive process, blood circulation, and respiration.

Low levels of Serotonin can case a number of health problems, but so too can excessively high levels. In extreme cases, Serotonin toxicity can be fatal.

The amount of Serotonin naturally produced in the body could not cause Serotonin Syndrome. However, when administering exogenous Serotonin agonists (like SSRI medications), there is potential for this adverse reaction.

Causes of Serotonin Syndrome

Serotonin toxicity most often occurs when an individual takes two drugs that affect Serotonin levels at the same time. The simultaneous use of such drugs can cause the body to release excessive amounts of Serotonin or to retain too much Serotonin in the brain.

Serotonin Syndrome is more likely to occur when a patient first starts a medication or increases the dosage.

Many medications affect Serotonin levels in the body, including triptans for migraines, and selective Serotonin reuptake inhibitors (SSRIs) or selective Serotonin/Norepinephrine reuptake inhibitors (SSNRIs) for depression.

SSRIs are the most commonly implicated medications in Serotonin toxicity, according to UpToDate by Wolters Kluwer. Commonly prescribed SSRIs include sertraline (Zoloft), fluoxetine (Prozac), and paroxetine (Paxil). Duloxetine (Cymbalta) is a popular SNRI.

Triptans are 5HT1 agonists, which means the molecules of this drug bind to the same receptors as Serotonin and stimulate the cell in the same way as Serotonin.

Triptans can constrict blood vessels in the same way as Serotonin, for example, which is why doctors recommend triptans to treat migraines caused by dilated blood vessels. Other effects of triptans may include the stabilization of some brain chemicals, a therapeutic effect that alleviates migraine attacks.

Other medications can cause Serotonin toxicity, including monoamine oxidase inhibitors (MAOIs) antidepressant medications, the painkiller meperidine (Demerol), and the cough medicine dextromethorphan.

The use of over-the-counter medications, illicit drugs or dietary supplements can also increase Serotonin levels. Combining non-prescription cough and cold medications that contain dextromethorphan with other drugs can lead to the syndrome, for example, as can using herbal supplements, including 5-HTP, L-Tryptophan, St. John’s wort, ginseng and nutmeg with other medications.

Using illicit drugs, including LSD, Ecstasy, cocaine and amphetamines alongside other medications may increase the risk for serotonin toxicity.

Serotonin Syndrome Symptoms

The symptoms and signs of Serotonin Syndrome form a triad of mental status change, autonomic hyperactivity, and neuromuscular abnormalities, according to the American College of Physicians.

Serotonin syndrome symptoms usually begin 6 to 24 hours after taking a medication, according to Drugs.com, and symptoms may continue for up to five weeks after discontinuation of the drug that caused the condition.

Symptoms may include:

• Irritation, restlessness
• Nausea and vomiting
• Diarrhea
• Fast heartbeat
• High blood pressure
• Rapid changes in blood pressure
• Hallucinations
• Increased body temperature
• Loss of coordination
• Overactive reflexes

When diagnosing Serotonin toxicity, practitioners consider the patient’s history of medication use, physical examination, and exclusion of other neurological disorders.

Doctors typically diagnose an individual with Serotonin Syndrome when the patient is taking a drug that changes the body’s Serotonin levels and when the person shows at least three of the following signs of Serotonin Syndrome:

• Agitation
• Diarrhea
• Heavy sweating not associated with physical activity
• Fever
• Mental status changes, including as confusion or a mild form of mania known as hypomania
• Muscle spasms, otherwise known as myoclonus
• Overactive reflexes, also known as hyperreflexia
• Shivering
• Tremor
• Uncoordinated movements, known as ataxia

Serotonin Syndrome Treatment

The most effective Serotonin Syndrome treatment depends largely on the severity of the patient’s symptoms. A doctor may suggest stopping involved medications to treat minor symptoms.

Moderately severe symptoms may require admission to a hospital for observation. Severe symptoms can require intensive treatment in a hospital.

Depending on the patient’s symptoms, doctors can prescribe various medications and treatments for Serotonin toxicity, including:

• Muscle relaxants, particularly benzodiazepines, to help control agitation, seizures and muscle stiffness
• Serotonin-production blocking agents, such as cyproheptadine, to halt the production of serotonin
• Oxygen to maintain normal oxygen levels in the blood
• Intravenous (IV) fluids to treat dehydration and fever
• Drugs to control heart rate and blood pressure
• A breathing tube and medication to paralyze the patient’s muscles if the individual has a high fever

How Long Does Serotonin Syndrome Last?

Less severe forms of Serotonin Syndrome usually resolve within 24 to 72 hours of stopping Serotonin-increasing medications or initiating the use of Serotonin-blocking medications.

Symptoms of Serotonin Syndrome caused by the use of certain antidepressants could take several weeks, however, as these medications remain in the body longer than do other drugs that cause Serotonin toxicity.

Early treatment reduces the risk for Serotonin Syndrome long-term effects. Complications of Serotonin Syndrome can include severe muscle breakdown and resulting kidney damage, according to the National Library of Medicine.

While the true incidence of Serotonin Syndrome is unknown, the condition has been observed in every type of patient, from newborn to the elderly.

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