Ondansetron:

It is a potent higly selective antagonist at the 5 hydroxytryptamine receptors sbtype 3 .

It can effectively control vomiting due to anticancer drugs as well as raitherapy .unlike metocloprmide ,

Ondansetron is not a lopomide antagonist and doesnot cause dystonia or extra pyramidal effects. 

It is a carbazole with causes antinauseant and antiemtic effects by selective and competitive blockade of the 5ht3 receptors .

Indication :

Vomiting and nausea associated with cytoxic radiotherapy and chemotherapy ,prophylaxis and treatment of postoperative vomiting andnausea