What is the Difference Between Neuroleptic Malignant Syndrome and Serotonin Syndrome

The key difference between neuroleptic malignant syndrome and serotonin syndrome is that neuroleptic malignant syndrome occurs due to the blocking of dopamine as a result of an adverse reaction to neuroleptic or antipsychotic drugs, while serotonin syndrome occurs when the body has too much serotonin as a result of taking medications such as antidepressants.

Neuroleptic malignant syndrome and serotonin syndrome are two rare medicine-induced neurological disorders. Some features of these disorders may overlap with each other. Therefore, diagnosis of them may be difficult. However, the neuroleptic malignant syndrome is usually characterized by lead-pipe rigidity, while serotonin is usually characterized by hyperreflexia and clonus.

CONTENTS

1. Overview and Key Difference
2. What is Neuroleptic Malignant Syndrome 
3. What is Serotonin Syndrome
4. Similarities – Neuroleptic Malignant Syndrome and Serotonin Syndrome
5. Neuroleptic Malignant Syndrome vs Serotonin Syndrome in Tabular Form
6. Summary – Neuroleptic Malignant Syndrome vs Serotonin Syndrome

What is Neuroleptic Malignant Syndrome?

Neuroleptic malignant syndrome (NMS) is a neurological disorder that occurs due to an adverse reaction that arises from neuroleptic or antipsychotic drugs used to treat diseases such as schizophrenia and bipolar disorder. This disorder is serious, but people can make a full recovery when it is diagnosed earlier. The neuroleptic malignant syndrome is more common in men than women. Moreover, some drugs that are used to treat nausea and vomiting also sometimes can cause NMS. The causes of NMS include antipsychotic drugs (chlorpromazine, fluphenazine, haloperidol, loxapine, aripiprazole, asenapine, brexpiprazole, etc.), nausea and vomiting medications (domperidone, droperidol, metoclopramide, prochlorperazine, etc.) and medications for Parkinson’s disease such as levopoda. All these medications block dopamine, which leads to the neuroleptic malignant syndrome.

The symptoms of NMS include high fever, muscle stiffness, sweating a lot, anxiety, fast and abnormal heartbeat, quick breathing, more saliva production than usual, kidney and heart failure, low oxygen in the body, aspiration pneumonia, and more acid in the body.

NMS can be diagnosed through physical signs, blood and urine tests, brain imaging scans, test for spinal fluid, and EEG to detect electrical problems in the brain. Furthermore, treatment options for NMS may include switching to a different antipsychotic drug,  reducing fever (antipyretic medicines), giving fluid and nutrition, giving muscle relaxants (dantrolene), giving drugs that produce too much dopamine (amantidine or bromocriptine), and giving a small electric current to improve symptoms.

What is Serotonin Syndrome?

Serotonin syndrome is a neurological disorder that occurs when the body has too much of a chemical called serotonin. It happens due to excessively taking medications such as antidepressants. The symptoms of this condition may include confusion, agitation, dilated pupils, headache, changes in blood pressure, nausea, vomiting, diarrhoea, fast and rapid heart rate, tremor, loss of muscle control, shivering and goosebumps, and heavy sweating.

The causes of serotonin syndrome include selective serotonin reuptake inhibitors (citalopram, escitalopram, etc.), serotonin and norepinephrine reuptake inhibitors (desvenlafaxine, desvenlafaxine succinate, etc.), monoamine oxidase inhibitors (isocarboxazid, phenelizine, etc.), drugs used for anxiety disorders (buspirone), drugs used for insomnia (trazodone), drugs used for migraine (almotriptan, naratriptan, etc.), certain pain medications (opioids), cough suppressants, and nausea medications (granisetron, metoclopramide, etc.).

Serotonin syndrome can be diagnosed through medical history, physical examination, lab tests to rule out tetanus, sepsis, encephalitis, or heart stroke. Furthermore, treatment options for serotonin syndrome may include removing the drugs that cause serotonin syndrome, giving intravenous fluid (IV), and taking medication such as cyproheptadine to keep the body from making serotonin.

What are the Similarities Between Neuroleptic Malignant Syndrome and Serotonin Syndrome?

• Neuroleptic malignant syndrome and serotonin syndrome are two rare medicine-induced neurological disorders.
• Both disorders can also be caused by nausea medications.
• These disorders are serious conditions if not treated well.
• Both disorders can be diagnosed through physical examination and blood tests.

What is the Difference Between Neuroleptic Malignant Syndrome and Serotonin Syndrome?

The neuroleptic malignant syndrome occurs due to the blocking of dopamine as a result of an adverse reaction to neuroleptic or antipsychotic drugs, while serotonin syndrome occurs when the body has too much serotonin because of taking some medications, such as antidepressants. Thus, this is the key difference between neuroleptic malignant syndrome and serotonin syndrome. Furthermore, NMS disease incidence is estimated to be 0.2-3.2% in a patient receiving neuroleptic drugs, while serotonin uptake disease incidence is estimated to be 14% to 16% who overdose antidepressants such as serotonin reuptake inhibitors (SSRIs).

The below infographic presents the differences between neuroleptic malignant syndrome and serotonin syndrome in tabular form for side-by-side comparison.

Summary – Neuroleptic Malignant Syndrome vs Serotonin Syndrome

Neuroleptic malignant syndrome and serotonin syndrome are two rare medicine-induced neurological disorders. Both these disorders are due to imbalances in chemical messengers in the body. The neuroleptic malignant syndrome occurs due to the blocking of dopamine. It happens due to an adverse reaction to neuroleptic or antipsychotic drugs. Serotonin syndrome occurs when the body has too much serotonin. It happens due to taking medications such as antidepressants. So, this is the key difference between neuroleptic malignant syndrome and serotonin syndrome.

Reference:

1. “Neuroleptic Malignant Syndrome.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services.
2. “Serotonin Syndrome: Symptoms, Causes, Diagnosis, Treatment.” WebMD.

Image Courtesy:

1.”SerotoninSyndrome” By Beckie Palmer – NCBI (CC BY 4.0) via Commons Wikimedia