Which of the following medications is commonly classified as an antibiotic?

Amoxicillin is commonly classified as an antibiotic because it is part of the penicillin group of medications and is primarily used to treat bacterial infections. It works by inhibiting the growth of bacteria, making it effective against a wide range of infections, including respiratory tract infections, ear infections, and urinary tract infections.

The other medications listed serve different purposes: Esmolol is a beta-blocker used primarily for managing heart rate and blood pressure; Diazepam is a benzodiazepine used for its anxiolytic, muscle relaxant, and sedative effects; and Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) utilized for pain relief, inflammation reduction, and fever control. Each of these medications plays an important role in their respective fields but does not fall into the category of antibiotics like amoxicillin.