The Neuroleptic Malignant Syndrome (NMS), alternatively referred to as the Antipsychotic Malignant Syndrome, is a potentially fatal condition that is infrequently observed and is linked to the administration of antipsychotic medications. This syndrome is characterized by a disturbance in consciousness, autonomic instability manifesting as hyperthermia, and muscular rigidity. The onset of this syndrome is typically within the initial month of treatment or following an escalation in the dosage of an antipsychotic medication. This case report delineates a case where NMS was precipitated by an excessive intake of haloperidol, a typical antipsychotic drug.

In the Emergency Department (ED), a 23-year-old male was admitted following an overdose of haloperidol, a typical antipsychotic drug. The patient exhibited symptoms of tachypnea and tachycardia, and initially presented with hypotension. His level of consciousness was variable, but maximal upon stimulation. Notably, there was a significant increase in muscle tension, characterized by cogwheel rigidity. His body temperature rose to 38.6 degrees Celsius. Laboratory findings revealed a substantial high anion gap metabolic acidosis, with a lactate level of 21.2 mmol/L. Additionally, his creatine kinase level was elevated, measuring 1347 U/L. The therapeutic approach encompassed the intravenous administration of midazolam (2.5 mg), lorazepam (2.5 mg), and biperiden (5 mg), in conjunction with resuscitation involving 2 liters of 0.9% NaCl. The patient demonstrated a positive response to this regimen, leading to his admission to the ward. Following a full recovery, he was discharged from the hospital the subsequent day.

The patient in our case fulfilled all the diagnostic criteria for NMS as stipulated in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V). NMS is not contingent on the dosage, although an increased dosage does elevate the risk. A thorough review of existing literature did not yield any cases mirroring ours.

In conclusion, we present a case where NMS developed after an overdose of haloperidol.