antagonists: 5-ht3 antagonists produce their anti emetic effect by blocking of the amplifying effect of serotonin on peripheral and central 5-ht3 receptors located on the various vagal afferent nerve endings and the chemoreceptor trigger zone. they are effective in the treatment and prophylaxis of cinv as well as in malignant bowel obstruction and kidney failure which are associated with elevated serotonin levels. these substances include dolasetron, granisetron, ondansetron, palonosetron, and tropisetron. they are often used in combination with other anti emetic drugs in people with high risk of emesis or nausea and are recommended as the most effective anti emetics in the prophylaxis of acute cinv. corticosteroids: such as dexamethasone are used in the treatment of emesis as a result of chemotherapy, malignant bowel obstruction, raised intracranial pressure and in the chronic nausea of advanced cancer, though their exact mode of action remain unclear. dexamethason is recommended for use in the acute prevention of highly, moderately, and low emetogenic chemotherapy and in combination with aprepitant for the prevention of delayed emesis in highly emetogenic chemotherapy. nk1 receptor antagonists: such as aprepitant block the nk1 receptor in the brainstem and gastrointestinal tract. their antiemetic activity when added to a 5-ht3 receptor antagonist plus dexametasone has been shown in several phase ii double-blind studies. cannabinoids: are a useful adjunct to modern anti emetic therapy in selected patients. they show a combination of weak anti emetic efficacy with potentially beneficial side effects such as sedation and euphoria. however, their usefulness is generally limited by the high incidence of toxic effects, such as dizziness, dysphoria, and hallucinations. some studies have shown that cannabinoids are slightly better than conventional anti emetics such as metoclopramide, phenothiazines and haloperidol in the prevention of nausea and vomiting. cannabinoids are an option in affected people who are intolerant or refractory to 5-ht3 antagonists or steroids and aprepitant as well as in refractory nausea and vomiting and rescue anti emetic therapy. prokinetic agents such as metoclopramide dopamine receptor antagonists such as phenothiazines (prochlorperazine and chlorpromazine), haloperidol, olanzapine, and levomepromazine, block d2 receptors found in the chemoreceptor trigger zone antihistaminic agents like promethazine block h1 receptors in the vomiting center of the medulla, the vestibular nucleus, and the chemoreceptor trigger zone anticholinergic agents such as scopolamine (hyoscine) are used as anti emetics as they relax smooth muscle and reduce gastrointestinal secretions by blockade of muscarinic receptors. they may be useful in the management of terminal bowel obstruction somatostatin analoga such as octreotide are used for the palliation of malignant bowel obstruction, especially when there is high output vomiting not responding to other measures cannabidiol is used as a palliative treatment (non-curative symptomatic treatment) and improves numerous symptoms that frequently appear during chemotherapy like nausea, vomiting, loss of appetite, physical pain or insomnia. due to the large number of cannabinoid receptors ( cb1 and cb2 ) distributed throughout the gastrointestinal tract ( gi ), these substances can help to control and treat many gi diseases where vomiting and nausea are frequent. other measures other non-drug measures may include: diet: small palatable meals are normally tolerated better than big meals in people affected by nausea and vomiting in cancer. carbohydrate meals are better tolerated than spicy, fatty and sweet foods. cool, fizzy drinks are found to be more palatable than still or hot drinks. the avoidance of environmental stimuli, such as sights, sounds, or smells that may initiate nausea. behavioral approaches, such as distraction, relaxation training and cognitive behavioural therapy may also be useful. alternative medicine: acupuncture and ginger have been shown to have some anti emetic effects on chemotherapy-induced emesis and anticipatory nausea, but have not been evaluated in the nausea of far advanced disease. palliative surgery palliative care is the active care of people with advanced, progressive illness such as cancer. the world health organization (who) defines it as an approach that improves the quality of life of patients and their families facing the problems associated with life-threatening illness, through the prevention and relief of suffering by means of early identification and impeccable assessment and treatment of pain and other problems (such as nausea or vomiting), physical, psychosocial, and spiritual. sometimes it is possible or necessary to provide relief for cancer caused nausea and vomiting through palliative surgical intervention. surgery is however not routinely carried out when there are poor prognostic criteria for surgical intervention such as intra-abdominal carcinomatosis, poor performance status and massive ascites. the surgical approach proves beneficial in affected people with operable lesions, a life expectancy greater than 2 months and good performance status. often a malignant bowel obstruction is the cause of the symptoms in which case the purpose of palliative surgery is to relieve the symptoms of bowel obstruction by means of several procedures including: stoma formation bypass of the obstruction resection of bowel segments placement of stents. percutaneous endoscopic gastrostomy (peg) tube placement to enable gastric venting. gastric venting through a nasogastric tube is a semi-invasive possibility for palliation of nausea and vomiting due to gastrointestinal obstruction in people with abdominal malignancies who decline surgery or where surgery may not be indicated. however nasogastric tubes are not recommended to be used over a long period of time because of the high risk of displacement, poor tolerance, restrictions in daily routine activities, coughing, clearing pulmonary secretions and can be cosmetically unacceptable and confining. complications of nasogastric tubes include aspiration, hemorrhage, gastric erosion, necrosis, sinusitis and otitis. epidemiology 12.7 million new cancer cases and 7.6 million cancer deaths were estimated worldwide in 2008. nausea or vomiting occur in 50 to 70% of people with advanced cancer. 50 to 80% of people undergoing radiotherapy experience nausea and/or vomiting, depending on the site of irradiation. anticipatory nausea and vomiting is experienced by approximately 20 to 30% of people undergoing chemotherapy. chemotherapy-induced nausea and vomiting resulting from treatment with highly emetogenic cytotoxic drugs can be prevented or effectively treated in 70 to 80% of affected people.