What should a nurse do if a client has a reaction to IV ampicillin?

When a client exhibits a reaction to IV ampicillin, stopping the infusion immediately is the appropriate action. This is critical because reactions can range from mild to severe, including allergic reactions that could lead to anaphylaxis. By halting the medication, the nurse prevents the ongoing exposure to the allergen, which could exacerbate the patient's symptoms.

Following the discontinuation of the infusion, the nurse would then need to monitor the client's vital signs closely to assess for any further changes that may indicate the severity of the reaction. Administering an antihistamine is a potential step in managing an allergic reaction, but it is secondary to immediately stopping the administration of the offending drug. In the case of a severe reaction, such as anaphylaxis, calling a code blue is warranted, but the immediate priority is to stop the medication to mitigate further risks to the patient.