Which medication is classified as a neurokinin 1 receptor antagonist?

Aprepitant is classified as a neurokinin 1 (NK1) receptor antagonist. This medication is primarily used to prevent nausea and vomiting caused by chemotherapy and is often administered as part of a broader antiemetic regimen. It works by blocking the action of substance P, a neuropeptide that binds to NK1 receptors in the brain, thereby reducing the symptoms associated with acute and delayed nausea and vomiting.

In the context of the other options, Palonosetron is a selective serotonin 5-HT3 receptor antagonist, Dronabinol is a cannabinoid used to treat nausea and stimulate appetite, and Compazine is an antipsychotic primarily used as an antiemetic that works through different receptor pathways, predominantly dopamine receptors. Therefore, none of these alternatives act directly on the neurokinin 1 receptors like Aprepitant does.