BACKGROUND: Suicidal thoughts and attempts are commonly observed among patients with depression. The presence of concomitant psychotic symptoms in a patient with an existing depression increases the risk of drug-drug interactions, especially in cases when multiple drugs are used for treatment.

CASE PRESENTATION: This case report describes a young adult female with a history of psychosis and depression, for which she had been taking risperidone and sertraline for the past six months. She was brought to the hospital by her family members after an alleged suicide attempt using her psychiatric medications. On examination, the patient exhibited disturbed consciousness and a moderately elevated body temperature, but notably, no muscle rigidity.

These clinical features suggested a mild form of serotonin syndrome (SS). Despite a 1500 mg sertraline overdose, which would typically result in symptoms such as severe agitation, hallucinations, sweating, flushing, or tremors, the patient's SS was unexpectedly mild considering the amount of drugs ingested.

CONCLUSION:   It was concluded that the patient developed serotonin syndrome (SS) due to a toxic overdose of sertraline. However, the severity of SS was mitigated by the concurrent ingestion of an equivalent dose of risperidone, a serotonin receptor antagonist. As a result, the condition was classified as mild to moderate SS, which, despite the large dose of the selective serotonin reuptake inhibitor, did not necessitate the use of an antidote.