Differential Diagnosis
- Single most likely diagnosis
- Anticholinergic toxicity (e.g., due to diphenhydramine or other anticholinergic substances): The patient's symptoms, such as sleepiness, hot and dry skin, dry mucous membranes, decreased bowel sounds, and dilated pupils, are consistent with anticholinergic toxicity. The presence of unlabeled pills at the party and the patient's altered mental status support this diagnosis.
- Other Likely diagnoses
- Serotonin syndrome: Given the patient's recent initiation of fluoxetine, a selective serotonin reuptake inhibitor (SSRI), and the potential for other substances to interact with it, serotonin syndrome is a possible diagnosis. Symptoms such as altered mental status, tachycardia, and hyperthermia are consistent with this condition.
- Alcohol or cannabis withdrawal: Although less likely, the patient's history of occasional alcohol and cannabis use raises the possibility of withdrawal, which could contribute to his altered mental status and autonomic instability.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Opioid overdose: Despite the lack of specific symptoms suggestive of opioid use, the presence of unlabeled pills and the patient's altered mental status necessitate consideration of opioid overdose, which can be fatal if not promptly treated.
- Aspirin or acetaminophen toxicity: Although less likely given the clinical presentation, the potential for severe consequences if missed (e.g., liver failure in acetaminophen overdose or severe metabolic acidosis in aspirin overdose) warrants consideration of these diagnoses.
- Rare diagnoses
- Neuroleptic malignant syndrome (NMS): Although rare, NMS can occur in patients taking certain medications, including SSRIs like fluoxetine. The patient's symptoms, such as altered mental status, hyperthermia, and autonomic instability, could be consistent with NMS.
- Infectious or inflammatory causes: Less likely given the context, but potential infectious or inflammatory causes (e.g., meningitis, encephalitis) should be considered, especially if the patient's condition worsens or does not respond to treatment for the suspected toxic or metabolic cause.