The practical nurse (PN) applies a preparation with keratolytic properties to both legs of a client with psoriasis. Which finding indicates that the desired effect has been achieved?

Choice A reason: Cephalexin, a cephalosporin, has a 5–10% cross-reactivity risk with penicillin allergies due to similar beta-lactam structures. An anaphylactic history increases the risk of severe reactions. Contacting the provider ensures safety, potentially leading to an alternative antibiotic to prevent life-threatening allergic responses.

Choice B reason: Monitoring for rash or hives is reactive and insufficient for a client with a penicillin anaphylaxis history. Cephalexin’s cross-reactivity risk requires proactive avoidance, not just observation, as anaphylaxis can occur rapidly, making this choice inadequate compared to provider consultation.

Choice C reason: Giving cephalexin with an antihistamine does not prevent anaphylaxis, which can be rapid and severe in penicillin-allergic clients. Antihistamines mitigate mild allergies but are ineffective against severe reactions. This choice is unsafe without confirming the drug’s appropriateness first.

Choice D reason: Administering cephalexin as prescribed ignores the significant risk of cross-reactivity with penicillin, given the client’s anaphylactic history. This could trigger a life-threatening reaction, as cephalosporins share structural similarities with penicillins, making immediate administration without verification dangerous.

Choice A reason: Diphenhydramine does not facilitate rapid transfusion. It is an antihistamine used to prevent allergic reactions during transfusions, not to alter infusion speed. Rapid infusion depends on clinical protocols and patient tolerance, not antihistamine effects, making this choice incorrect.

Choice B reason: Diphenhydramine does not inhibit antigen-antibody reactions, which occur in transfusion mismatches. It mitigates histamine-mediated allergic symptoms, like itching or hives, but does not prevent immunological reactions. This choice is incorrect, as it misrepresents the drug’s role in symptom management.

Choice C reason: While diphenhydramine may cause sedation, its primary purpose before transfusion is to prevent allergic reactions, not to promote relaxation. Relaxation is a secondary effect, not the clinical rationale for its use, making this choice less accurate than allergy prevention.

Choice D reason: Diphenhydramine, an antihistamine, minimizes allergic reaction symptoms, such as itching or hives, during blood transfusions by blocking histamine receptors. This premedication reduces the risk of mild transfusion-related allergic responses, ensuring patient comfort and safety, making it the correct explanation.