Q. A 41-year-old female is brought to the emergency department by emergency medical services (EMS) after consuming approximately 50 ml of an insecticide in an apparent suicide attempt. While establishing intravenous (IV) access, paramedics noted her blood was dark brown in color. They also report co-oximetry levels of serum methemoglobin (MetHb) at 91 percent, carboxyhemoglobin (COHb) levels of less than 2 percent, and partial pressure of oxygen (PO2) of 80 mm Hg. No other information is available at this time. On physical examination, the patient is somnolent and cyanotic. Her heart rate is 160/min, blood pressure is 110/70 mm Hg, respiratory rate 30/min, and temperature 38.0 degrees Celsius (100 degrees Fahrenheit). Saturation measured by pulse oximetry is 80 percent on 100 percent oxygen. The remaining physical examination is unremarkable for signs of trauma, rashes, or lesions. Which of the following medications is most indicated at this time?