Which drug is classified as an opioid?

Oxycodone is classified as an opioid because it is a powerful analgesic that acts on the central nervous system to relieve pain. Opioids are substances that bind to specific receptors in the brain and body to produce effects such as pain relief, sedation, and euphoria. Oxycodone, like other opioids, is derived from the opiate class and is used medically for managing moderate to severe pain.

In contrast, the other choices do not belong to the opioid class. Ketamine is primarily used as an anesthetic and has dissociative properties. Diazepam is a benzodiazepine, commonly prescribed for anxiety and seizures, while phenobarbital is a barbiturate, primarily used as an anticonvulsant. Each of these substances works through different mechanisms and has distinct effects on the body.