<unk>  is classified as an NK1 antagonist because it blocks signals given off by NK1 receptors. This, therefore, decreases the likelihood of vomiting in patients. NK1 is a G protein-coupled receptor located in the central and peripheral nervous system. This receptor has a dominant ligand known as Substance P (SP). SP is a neuropeptide, composed of 11 amino acids, which sends impulses and messages from the brain. It is found in high concentrations in the vomiting center of the brain, and, when activated, it results in a vomiting reflex. In addition to this it also plays a key part in the transmission of pain impulses from the peripheral receptors to the central nervous system.<unk>  has been shown to inhibit both the acute and delayed emesis induced by cytotoxic chemotherapeutic drugs by blocking substance P landing on receptors in the brain's neurons. Positron emission tomography (PET) studies, have demonstrated that<unk>  can cross the blood brain barrier and bind to NK1 receptors in the human brain. It has also been shown to increase the activity of the 5-HT3 receptor antagonists ondansetron and the corticosteroid dexamethasone, which are also used to prevent nausea and vomiting caused by chemotherapy.<unk>  is taken orally in the form of a capsule. Before clinical testing, a new class of therapeutic agent has to be characterized in terms of preclinical metabolism and excretion studies. Average bioavailability is found to be around 60-65%.<unk>  is metabolized primarily by CYP3A4 with minor metabolism by CYP1A2 and CYP2C19. Seven metabolites of<unk> , which are only weakly active, have been identified in human plasma. As a moderate inhibitor of CYP3A4,<unk>  can increase plasma concentrations of co-administered medicinal products that are metabolized through CYP3A4. Specific interaction has been demonstrated with oxycodone, where<unk>  both increased the efficacy and worsened the side effects of oxycodone; however it is unclear whether this is due to CPY3A4 inhibition or through its NK-1 antagonist action. Following IV administration of a 14C-labeled prodrug of<unk>  (L-758298), which is converted rapidly and completely to<unk> , approximately 57% of the total radioactivity is excreted in the urine and 45% in feces. No unchanged substance is excreted in urine.
Aprepitant
Eptifibatide
Oprelvekin
Netupitant
Prasugrel
Defibrotide
Elinogrel
Ambrisentan