Case Presentation:
A 20 year‐old man presented to the emergency room (ER) in a state of agitated delirium. Review of electronic medical records showed a recent hospital discharge for bipolar disorder. His medications were olanazapine and lithium. He had also had a recent admission for delirium thought to be secondary to diphenhydramine and dextromethorphan ingestion. Upon exam in the ER, he was found in four‐point restraints. His vital signs showed that he was afebrile, tachycardic, and hypertensive. He was alert but not oriented; his speech was dysarthric. He was profusely sweating. On examination of the eyes he was noted to have mydriasis and ocular clonus. His extremities were flaccid to passive range of motion without cogwheeling or rigidity. His lower extremities were hyperreflexic. All four extremities were positive for spontaneous clonus with sustained clonus on ankle flexion. Creatine phosphokinase was elevated at 3,745 U/Liter. His lithium level was subtherapeutic at 0.37 mEq/liter. His urine drug screen was negative.
Discussion:
Managing patients with psychiatric problems and prescribing psychiatric medications are common actions preformed by the hospitalist. It is important to recognize the combined effects of these medications and how patients present when altered secondary to these medications. Serotonin alters temperature, behavior, and attention as well as causing vasoconstriction, bronchoconstriction, and increasing gastrointestinal motility. Serotonin syndrome can result from a single serotonergic agent or multiple agents together by causing stimulation of serotonin receptors.
Serotonin syndrome and neuroleptic malignant syndrome are medical emergencies associated with psychotropic administration. Differentiation of these syndromes can be complex. Diagnosis of serotonin syndrome is made using the Hunter Serotonin Toxicity Criteria which requires a patient to have taken a serotonin agent and meet one of the following criteria: sponataneous clonus, inducible clonus plus agitation or diaphoresis, ocular clonus plus agitation or diaphoresis, tremor plus hyperreflexia, or hypertonia plus hyperthermia plus ocular clonus or inducible clonus. Serotonin syndrome is often misdiagnosed as neuroleptic malignant syndrome. In serotonin syndrome the patient experiences neuromuscular hyperreactivity, whereas in neuroleptic malignant syndrome the neuromuscular responses are sluggish. Also, hyperreflexia and myoclonus are rare in neuroleptic malignant syndrome. Timing is also used to distinguish the two syndromes. Serotonin syndrome develops over twenty‐four hours and resolves in a similar time period. Neuroleptic malignant syndrome develops over days to weeks and resolves in about a week.
In this case, the patient’s physical exam met the Hunter Serotonin Toxicity Criteria, thus indicating a diagnosis of serotonin syndrome. The patient overdosed on dextromethorphan, a serotonin reuptake inhibitor. He was also taking lithium, which increases the postsynaptic receptor sensitivity to serotonin. This synergistic mechanism of action caused the patient to have serotonin syndrome.
Conclusions:
Hospitalists should be aware of interactions between highly abused drugs and prescribed serotonergic agents to avoid possible complications including serotonin syndrome. Also, hospitalists should consider the use of the Hunter Serotonin Toxicity Criteria to help with recognition of this syndrome.