A nurse is caring for a client who has streptococcal pneumonia and a prescription for penicillin G by intermittent IV bolus. 10 minutes into the infusion of the third dose, the client reports that the IV site itches and that he feels dizzy and short of breath. Which of the following actions should the nurse take first?

A. Elevate the head of the bed. – While elevating the head of the bed can aid breathing, it is not the priority action in this situation. B. Call the client's provider. – Notifying the provider is important, but the first action is to stop the offending agent causing the reaction. C. Auscultate the client's breath sounds. – Assessing breath sounds is appropriate but should be done after stopping the infusion, as the priority is to remove the source of the reaction. D. Stop the infusion. – The client is showing signs of a possible anaphylactic reaction (itching, dizziness, shortness of breath). The priority action is to stop the infusion immediately to prevent further exposure to the allergen and worsening of symptoms.