EM@3AM: Methemoglobinemia

A 42-year-old female with a past medical history of iron deficiency anemia presents to the ED with a peritonsillar abscess. You give 2 benzocaine sprays and successfully aspirate the abscess. As she is waiting for her discharge paperwork, the nurse alerts you that her oxygen saturation is now in the mid-80s. Repeat vitals in the room are as follows: BP 102/78, HR 102, O2 85%, RR 24. She has perioral cyanosis that was not seen on your initial exam. What is the diagnosis and best next step?