Adverse Effects of Vancomycin The main concern with vancomycin is Hypersensitivity (allergic or due to direct mast-cell degranulation) Vancomycin should be infused slowly in a dilute solution (2.5 to 5.0 mg / mL) over 60 minutes or more and at a rate no greater than 10 mg / minute to avoid vancomycin infusion reaction (a histamine-mediated reaction that can cause pruritus and flushing on the face, neck, and shoulders).