Ondem -MD 4 Tablet blocks the action of chemicals in the body that can make you feel or be sick. It is often used to prevent nausea and vomiting that may be caused by cancer chemotherapy and radiation treatment (in adults and children aged 4 years and older). It is usually taken both before and after chemotherapy or radiation. This medicine helps you recover more comfortably from these treatments. It is also effective at preventing nausea and vomiting after an operation (in adults only). The dose will depend on what you are being treated for but always take this medicine as it is prescribed.