A nurse is caring for a client who has cellulitis and is to begin antibiotic therapy. The client has a history of anaphylactic reaction to penicillin. Which of the following medications is contraindicated for this client?

A. "My appetite is increased." Diphenhydramine is an antihistamine that primarily treats allergic reactions by blocking histamine receptors. While antihistamines can sometimes cause increased appetite as a side effect, this is not an indicator of effectiveness in treating an allergic reaction.

B. "I don't have a headache anymore." While diphenhydramine may help with headaches due to its sedative and antihistamine effects, headache relief is not the primary goal when treating an allergic reaction. The effectiveness of diphenhydramine in this scenario should be assessed based on improvements in allergic symptoms rather than headache relief.

C. "My voice is no longer hoarse." Hoarseness can be a sign of airway involvement due to allergic reaction-related swelling (laryngeal edema). Diphenhydramine reduces histamine-induced inflammation, which can help resolve airway symptoms. Improvement in hoarseness suggests reduced swelling and a lower risk of airway obstruction, making this the best indicator of effectiveness.

D. "I am feeling more alert." Diphenhydramine commonly causes drowsiness due to its sedative effects. Feeling more alert would be an unusual response to the medication and does not indicate improvement in the allergic reaction. The primary concern is symptom resolution, particularly respiratory symptoms, rather than changes in alertness.

A. Rash. A rash while taking allopurinol can indicate a serious hypersensitivity reaction, including Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN). These life-threatening conditions involve widespread skin blistering, mucosal involvement, and systemic symptoms. Immediate discontinuation of allopurinol and medical intervention are required to prevent severe complications.

B. Diarrhea. Mild gastrointestinal disturbances, including diarrhea, are common with allopurinol use. While bothersome, diarrhea is not life-threatening and can often be managed by adjusting the dose or taking the medication with food. It does not require immediate discontinuation unless severe or persistent.

C. Nausea. Nausea is a common, mild side effect of allopurinol that usually resolves with time or by taking the medication after meals. It is not an emergency and does not require urgent intervention unless accompanied by other concerning symptoms such as vomiting or severe abdominal pain.

D. Metallic taste in mouth. A metallic taste can occur with allopurinol use but is not harmful. It is a minor side effect that does not indicate toxicity or severe adverse reactions. Clients can be reassured that this effect is temporary and not a reason to stop the medication.