Which of the following is classified as a barbiturate?

Amobarbital is classified as a barbiturate, which is a class of drugs derived from barbituric acid. Barbiturates are central nervous system depressants that can induce sedation, relieve anxiety, and provide sleep. They were commonly used in the past for the treatment of anxiety and sleep disorders but have largely been replaced by benzodiazepines and other medications due to their potential for dependence and overdose.

Other options listed do not fall into the barbiturate category. Hydrocodone is an opioid analgesic used primarily to treat pain, while diazepam is a benzodiazepine used to treat anxiety, muscle spasms, and seizures. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) used to treat depression and anxiety disorders. Therefore, among the choices, Amobarbital is the only medication that is recognized as a barbiturate.