A 17-year-old with suspected infectious mononucleosis is afebrile and has acute otalgia. Which medication should be avoided?

In cases of infectious mononucleosis, particularly when caused by the Epstein-Barr virus (EBV), the use of amoxicillin should be avoided due to the risk of developing a rash. This is especially significant in adolescents, as up to 90% of individuals with mononucleosis who are treated with amoxicillin or ampicillin develop a widespread, morbilliform rash. The rash can be confusing and could lead to misdiagnosis of an allergic reaction when it is actually a consequence of the viral infection in the setting of antibiotic use.

Other medications mentioned, such as Zithromax (azithromycin), cefdinir, and Bactrim (trimethoprim/sulfamethoxazole), do not carry the same risk of rash association with EBV. Therefore, while they can be used in managing secondary infections or symptoms, amoxicillin is explicitly contraindicated in patients with suspected infectious mononucleosis to prevent unnecessary complications related to the rash.