Serotonin Syndrome Triggered by Overuse of Caffeine and Complicated With Neuroleptic Malignant Syndrome: A Case Report

Serotonin syndrome is a rare complication occurring in patients with psychiatric disorders that are treated with selective serotonin reuptake inhibitors (SSRIs). There are various triggers for serotonin syndrome, including non-SSRI antidepressants. In rare cases, serotonin syndrome may be triggered by nonmedicinal foods, such as coffee. The patient described in this case report was a 65-year-old woman with a past medical history of major depression and a diagnosis of Parkinson's disease who presented to our medical center with chief complaints of nausea, vomiting, and drowsiness. She had previously been prescribed paroxetine hydrochloride hydrate for depression, and she was prescribed levodopa and carbidopa for Parkinson's disease. She also drank 20 cups of coffee in a short period of time two days prior to admission due to excessive sleepiness. She was diagnosed with serotonin syndrome based on her clinical symptomology, which included diaphoresis, mydriasis, fine tremor, myoclonus, hypertension, and tachycardia. She was treated with diazepam and cyproheptadine hydrochloride hydrate. Later, she experienced muscle pain with increased creatinine kinase levels after she failed to take levodopa and carbidopa. These findings were suggestive of neuroleptic malignant syndrome. The patient was treated with supportive care. Excessive coffee intake triggers serotonin syndrome by promoting 5-hydroxytryptamine (serotonin) secretion. Patients with psychiatric diseases that necessitate treatment with SSRIs should be educated regarding caffeine consumption. Moreover, patients presenting with agitation and drowsiness should be evaluated for serotonin syndrome within the differential diagnosis. Patients with depression and Parkinson's syndrome should be evaluated for associated comorbidities, particularly serotonin syndrome and neuroleptic malignant syndrome.