Which of the following is NOT classified as an opioid?

Aspirin is not classified as an opioid because it is a non-opioid analgesic and anti-inflammatory medication. Opioids are a class of drugs that work by binding to specific receptors in the central nervous system to relieve pain, while aspirin works by inhibiting the enzyme cyclooxygenase (COX), which plays a role in the inflammatory process and pain perception.

In contrast, fentanyl, hydromorphone, and oxycodone are all opioids that are derived from opium and are primarily used for pain management. They function through different mechanisms in the body, specifically targeting opioid receptors to provide analgesic effects. Understanding these classifications is crucial for effective pain management and ensuring safe medication use in various clinical scenarios.