Survival Following a Tricyclic Antidepressant Overdose Presenting With Serotonin Syndrome-Like Symptoms and Critical Illness Polyneuropathy: A Case Report

We report the case of a patient who ingested a lethal dose of amitriptyline, presented with serotonin syndrome-like neurological symptoms on arrival, and subsequently developed suspected critical illness polyneuropathy (CIP) during the clinical course. A 54-year-old man with a history of depression intentionally ingested approximately 2,250 mg of amitriptyline in a single dose. On arrival, he exhibited altered consciousness, hyperthermia, metabolic acidosis, and QRS prolongation, necessitating the immediate initiation of mechanical ventilation and intravascular cooling. Despite sedation, myoclonus emerged, raising suspicion of serotonin syndrome based on the presence of hyperthermia, myoclonus, and altered mental status. Clonazepam, levetiracetam, and cyproheptadine were administered, along with alkalinization therapy. During hospitalization, the patient developed aspiration pneumonia that progressed to acute respiratory distress syndrome, requiring prone positioning and prolonged mechanical ventilation. Profound respiratory muscle weakness necessitated tracheostomy. Subsequently, limb weakness and nerve conduction study findings raised suspicion for CIP. This case highlights that tricyclic antidepressant intoxication can manifest with diverse neurological and neuromuscular complications, necessitating comprehensive management from the acute through chronic phases.