Causes

Excessive accumulation of serotonin in your body creates the symptoms of serotonin syndrome.

Under normal circumstances, nerve cells in your brain and spinal cord produce serotonin that helps regulate your attention, behavior and body temperature.

Other nerve cells in your body, primarily in your intestines, also produce serotonin. Serotonin plays a role in regulating your digestive process, blood flow and breathing.

Although it's possible that taking just one drug that increases serotonin levels can cause serotonin syndrome in susceptible individuals, this condition occurs most often when you combine certain medications.

For example, serotonin syndrome may occur if you take an antidepressant with a migraine medication. It may also occur if you take an antidepressant with an opioid pain medication.

Another cause of serotonin syndrome is intentional overdose of antidepressant medications.

A number of over-the-counter and prescription drugs may be associated with serotonin syndrome, especially antidepressants. Illicit drugs and dietary supplements also may be associated with the condition.

The drugs and supplements that could potentially cause serotonin syndrome include:

• Selective serotonin reuptake inhibitors (SSRIs), antidepressants such as citalopram (Celexa), fluoxetine (Prozac, Sarafem), fluvoxamine, paroxetine (Paxil, Pexeva, Brisdelle) and sertraline (Zoloft)
• Serotonin and norepinephrine reuptake inhibitors (SNRIs), antidepressants such as duloxetine (Cymbalta, Drizalma Sprinkle) and venlafaxine (Effexor XR)
• Bupropion (Zyban, Wellbutrin SR, Wellbutrin XL), an antidepressant and tobacco-addiction medication
• Tricyclic antidepressants, such as amitriptyline and nortriptyline (Pamelor)
• Monoamine oxidase inhibitors (MAOIs), antidepressants such as isocarboxazid (Marplan) and phenelzine (Nardil)
• Anti-migraine medications, such as carbamazepine (Tegretol, Carbatrol, others), valproic acid (Depakene) and triptans, which include almotriptan, naratriptan (Amerge) and sumatriptan (Imitrex, Tosymra, others)
• Pain medications, such as opioid pain medications including codeine, fentanyl (Duragesic, Abstral, others), hydrocodone (Hysingla ER, Zohydro ER), meperidine (Demerol), oxycodone (Oxycontin, Roxicodone, others) and tramadol (Ultram, ConZip)
• Lithium (Lithobid), a mood stabilizer
• Illicit drugs, including LSD, ecstasy, cocaine and amphetamines
• Herbal supplements, including St. John's wort, ginseng and nutmeg
• Over-the-counter cough and cold medications containing dextromethorphan (Delsym)
• Anti-nausea medications such as granisetron (Sancuso, Sustol), metoclopramide (Reglan), droperidol (Inapsine) and ondansetron (Zofran, Zuplenz)
• Linezolid (Zyvox), an antibiotic
• Ritonavir (Norvir), an anti-retroviral medication used to treat HIV