Which of the following is NOT an analgesic?

The correct answer is penicillin, which is not an analgesic. Analgesics are medications that are specifically used to relieve pain. Fentanyl, acetaminophen, and ibuprofen are all recognized for their pain-relieving properties.

Fentanyl is a powerful synthetic opioid that is used for managing severe pain, often in a medical setting. Acetaminophen, commonly known as Tylenol, is an over-the-counter medication that reduces pain and fever. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that not only helps relieve pain but also reduces inflammation and fever.

On the other hand, penicillin is an antibiotic used to treat bacterial infections and does not have any properties related to pain relief. It works by targeting and inhibiting the growth of bacteria, which is entirely different from the function of analgesic medications. Thus, this distinction in function clarifies why penicillin is classified separately from analgesics.