Differential Diagnosis for Acute Confusion and Autonomic Instability

The patient's presentation of acute confusion, dilated pupils, fever, high blood pressure, anxiety, tremor, and sweating after ingesting a full pack of fluoxetine tablets suggests a complex clinical picture. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Serotonin Syndrome: This condition is caused by an excess of serotonin in the central nervous system, which can occur due to the ingestion of certain medications, including selective serotonin reuptake inhibitors (SSRIs) like fluoxetine. The patient's symptoms, such as confusion, dilated pupils, fever, hypertension, anxiety, tremor, and sweating, are classic for serotonin syndrome, especially given the recent ingestion of a large dose of fluoxetine.

• Other Likely Diagnoses

  • Anticholinergic Toxicity: Although less likely given the specific medication involved, anticholinergic toxicity can present with similar symptoms such as confusion, dilated pupils, fever, and autonomic instability. However, fluoxetine is not typically associated with significant anticholinergic effects.
  • Sympathomimetic Toxicity: The ingestion of certain substances can lead to sympathomimetic toxicity, characterized by symptoms like hypertension, tachycardia, dilated pupils, and sweating. While fluoxetine is primarily a serotonergic agent, its overdose can lead to some sympathomimetic effects.

• Do Not Miss Diagnoses

  • Neuroleptic Malignant Syndrome (NMS): Although NMS is more commonly associated with the use of antipsychotic medications, it can present with fever, autonomic instability, and altered mental status. The key to distinguishing NMS from serotonin syndrome lies in the medication history and the presence of rigidity, which is more characteristic of NMS.
  • Intracranial Hemorrhage or Other Neurological Emergencies: The acute onset of confusion and autonomic instability could also suggest a neurological emergency such as an intracranial hemorrhage. While less directly related to fluoxetine overdose, these conditions are critical and require immediate diagnosis and treatment.

• Rare Diagnoses

  • Thyroid Storm: This is a life-threatening condition that involves an extreme exacerbation of thyrotoxicosis symptoms, which can include fever, tachycardia, hypertension, and altered mental status. It is a rare condition and would be less likely in this context without a history of thyroid disease.
  • Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of hypertension, tachycardia, sweating, and anxiety. However, this diagnosis would not directly relate to the ingestion of fluoxetine and would require additional diagnostic evidence.