A 45-year-old man presents to the emergency department with cellulitis of his left leg. He is being treated with vancomycin. Ten minutes after the infusion is initiated, he complains of intense pruritus and lightheadedness. Erythema is noted on his face and neck. Which of the following is the next best step in the management of this patient?
A Administer intramuscular epinephrine and decrease the rate of the infusion
B Administer intramuscular epinephrine and suspend the infusion
C Administer intravenous diphenhydramine and decrease the rate of the infusion
D Administer intravenous diphenhydramine and suspend the infusion