Double-Edged Sword

A 35-year-old woman is brought to the emergency department by ambulance after collapsing at home. Earlier in the day, her primary care doctor examined her and prescribed amoxicillin for her sinusitis. Paramedics report blood pressure 70/30 mm Hg, heart rate 140 /min, respiratory rate 40/min, and oxygen saturation 76%. Intravenous fluids and oxygen were administered during transport. Despite bag-valve-mask ventilation, her oxygen saturation remains low. On the physical examination, she is obtunded and shows perioral cyanosis, tongue swelling, stridor, wheezing, and laboured breathing. Her skin is cool and clammy with large urticarial lesions.