Which of the following is identified as an appetite suppressant?

Dextroamphetamine is recognized as an appetite suppressant due to its central nervous system stimulant properties. It works by affecting neurotransmitters in the brain, particularly increasing the release of norepinephrine and dopamine, which can lead to an increased sense of alertness and energy while also reducing feelings of hunger. This mechanism is beneficial for weight loss treatments and makes it effective for individuals looking to manage their weight by suppressing appetite.

Other medications listed, while they have roles in weight management or metabolic processes, do not primarily function as appetite suppressants. Orlistat, for instance, works by inhibiting fat absorption in the gut but does not directly influence appetite. Metformin is primarily used to manage blood sugar levels in type 2 diabetes and may have a secondary effect on weight management but does not act as an appetite suppressant. Phenelzine, an antidepressant, is part of the monoamine oxidase inhibitor class and focuses on mood regulation rather than appetite control.