Serotonin syndrome is a disorder caused by drug induced excess of intra-synaptic 5-hydroxytryptamine (5-HT). Combination of drugs with different mechanisms of action is the most common cause of the reaction.

To report a case of serotonin syndrome in order to underline the interactions between antidepressant and pain relief medication.

Case study and description of a patient treated in out-patient clinic.

A 48 year old gentleman was referred to a community mental health team for review of his depressive disorder and medication. The patient had a 15 year history of recurrent depressive disorder and a 10 year history of chronic back pain and migraine. The patient had been on medication for both conditions requiring frequent changes in drugs and doses. A recent episode of depression was managed by changing from sertraline to venlafaxine. His pain relief medication included sumatriptan and tramadol. He soon experienced agitation, confusion, restlessness, dry mouth, and sweatiness. The symptoms worsened for 10 days until the patient stopped venlafaxine and returned to sertraline.

In patients with chronic pain and depression a detailed drug history and awareness from clinicians to the risk of serotonin syndrome are vital due to potentially fatal complications.