Neuroleptic malignant syndrome due to promethazine

Area of Science:

• Clinical Toxicology
• Pharmacology
• Emergency Medicine

Background:

• Neuroleptic Malignant Syndrome (NMS) is a rare but life-threatening condition.
• It is typically associated with antipsychotic medications.
• This case explores a potential association with promethazine.

Observation:

• A 42-year-old male presented with severe hyperthermia (42.4°C), diaphoresis, delirium, labile blood pressure, tachycardia, tachypnea, muscle rigidity, and incontinence.
• The patient had recently been prescribed promethazine for abdominal pain, nausea, and vomiting.
• Initial presentation mimicked other hypermetabolic states.

Findings:

• Laboratory results revealed leukocytosis, hypernatremia, metabolic acidosis, elevated creatinine phosphokinase, elevated transaminases, azotemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and myoglobinuria.
• The constellation of clinical and laboratory findings strongly indicated Neuroleptic Malignant Syndrome.
• Promethazine was identified as the likely causative agent.

Implications:

• This case underscores the potential for promethazine to induce Neuroleptic Malignant Syndrome.
• Clinicians should consider NMS in patients presenting with hyperthermia and autonomic instability, even with less common offending agents.
• Prompt recognition and management are crucial for patient outcomes in NMS.