Final answer:
The patient's symptoms are consistent with drug-induced serum sickness, a type III hypersensitivity reaction. Discontinuation of the medication and medical evaluation are recommended. Treatment may involve supportive care and corticosteroids.
Step-by-step explanation:
The symptoms described by the patient, including fever, urticaria, and polyarthralgia, are consistent with a type III hypersensitivity reaction known as drug-induced serum sickness. This reaction can occur as a result of an immune response to medications such as penicillin and bactrim. It typically manifests with systemic symptoms such as fever, rash, and joint pain, without mucosal involvement. The symptoms may occur a few weeks after starting the medication.
It is important for the patient to discontinue the medication and seek medical attention for further evaluation and management. Treatment may include supportive care, such as antipyretics and analgesics for fever and pain relief, as well as corticosteroids to suppress the immune response.