Letters to the Editor
Venlafaxine-Induced Delirium
Dear Editor:
Venlafaxine has been associated with delirium but, typically, only in the context of serotonin syndrome. We are aware of only a single report of isolated delirium attributable to venlafaxine (1). Venlafaxine inhibits serotonin and norepinephrine reuptake. It is also a weak inhibitor of dopamine reuptake. Interestingly, venlafaxine has one of the highest incidences of precipitating serotonin syndrome and has even been shown to elicit serotonin syndrome on its own (2,3). We report a case of isolated delirium in an individual receiving venlafaxine and ibuprofen.
Case Report
Ms A, aged 46 years, presented to the emergency department disoriented, with auditory hallucinations, loose associations, irritability, and a disorganized thought process. Collateral history revealed that the onset of symptoms developed suddenly, in the previous 36 hours. Her medical history was noncontributory. Her psychiatric history included dysthymia and alcohol dependence, although she claimed to have abstained from alcohol for the past 5 years. She had a long history of ibuprofen consumption (600 mg orally 3 times daily) and felt that this helped her with irritability and reduced her craving for nicotine. Approximately 4 weeks prior to presenting, she was started on venlafaxine 37.5 mg orally each morning and 75 mg orally at bedtime, for depression. She was given a sample of venlafaxine and admitted to taking more than the recommended amount, owing to an unclear understanding of the prescribed dosage.
Other causes of delirium were investigated through examination and laboratory values. Her initial blood pressure was 170/94, with a subsequent recording of 140/79. The rest of her physical and neurological exam was within normal limits. Blood alcohol level was undetected, and other laboratory values, including thyroid-stimulating hormone (TSH), complete blood count (CBC), and a basic metabolic panel, were essentially normal. Regrettably, a serum venlafaxine level was not drawn.
Ms A was admitted to the psychiatric unit and started on venlafaxine (extended release) 150 mg daily and olanzapine 5 mg daily at bedtime. Two days after admission, the patient’s delirium resolved and she was discharged on venlafaxine (extended release) 150 mg daily. Discontinuation of ibuprofen was advised. Follow-up 6 weeks later revealed no residual effects of the delirium.
The delirium illustrated in Ms A was most likely produced by high levels of venlafaxine. To our knowledge, there is no literature to support the idea that ibuprofen interacts with venlafaxine; however, it is plausible, considering that both are metabolized by the liver. Whether this patient’s delirium was on the continuum of serotonin syndrome, even though she clearly did not demonstrate autonomic instability or neuromuscular changes, remains unresolved. When high levels of venlafaxine are suspected, a high index of suspicion for serotonin syndrome and delirium is warranted. Owing to venlafaxine’s increased popularity, we encourage further investigation of the therapeutic index and potential drug interactions of venlafaxine.
References
1. Pfeffer F, Grube M. An organic psychosis due to a venlafaxine- propafenone interaction. International Journal of Psychiatry and Medicine 2001;31:433–41.
2. Kolecki P. Isolated venlafaxine-induced serotonin syndrome. J Emerg Med 1997;15:491–3.
3. Mason PJ, Morris VA, Balcezak TJ. Serotonin syndrome. Medicine (Baltimore) 2000;79:201–9.
Christopher Howe, Medical Student
Sajid Ravasia, MD
Fargo, North Dakota
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