- A recent systematic review  has identified evidence to support the use of metoclopramide and 5HT3 antagonists in advanced cancer. Other antiemetics are fequently used in palliative care, but at present lack a strong evidence base.
- The choice of an antiemetic for nausea may be either empirical, or aetiological - related to the likely main mechanism of nausea and / or vomiting. There is no evidence to support one approach over the other, based on a systematic review of randomised controlled trials. 
- Clinical practice guidelines for palliative management of malignant bowel obstruction are available. 
- It is likely that steroids hasten the resolution of bowel obstruction,  although this conclusion is based on very small studies and the effect size was small.
- The option of rectal or gastroduodenal stenting in malignant obstruction appears to offer good palliation in selected patients. [4-6]
Nausea can either be acute, or persistent and chronic, and is not always associated with vomiting. In many cases it is possible to identify a cause, although in the palliative care population nausea is frequently multifactorial.
Palliative conditions that frequently cause nausea and / or vomiting include intra-abdominal or gastrointestinal malignancies - especially those which result in bowel obstruction; central nervous system malignancy - which may cause raised intracranial pressure, cerebellar or vestibular symptoms; and HIV AIDS.
Other factors that contribute to nausea and / or vomiting that should be sought, and treated where possible, include:
- Metabolic imbalance, including hypercalcemia, uraemia, liver failure
- Sepsis (including urinary tract and respiratory tract infection)
- Conditions affecting gastrointestinal motility, including constipation, previous surgery, gastroparesis, or autonomic failure
- Reflux or peptic ulcer disease
- Medication and treatment side effects, including opioids and other drugs, chemotherapy, and radiotherapy
- Anxiety and depression, anticipatory nausea
- Inappropriate presentation of food.
More in this topic
Active research areas / controversies
- There are no widely accepted assessment tools for nausea and vomiting, particularly for research. Nausea must be self-assessed by patients, whereas vomiting can be monitored objectively. Nausea is routinely assessed in Australian palliative care services using Symptom Assessment Scores (SAS) which is part of the PCOC dataset.
- Despite widespread use in palliative care, there is currently no high level evidence supporting the use of haloperidol as an antiemetic. [1,7] Its use continues to be based on uncontrolled studies  and expert opinion. 
- No high level evidence was found to support the common clinical practice of avoiding prokinetic antiemetic drugs such as metoclopramide or domperidone in complete bowel obstruction, due to the possible risk of adverse effects including worsening abdominal pain. This recommendation continues to be based on expert opinion. 
- A systematic review of Nabilone (a cannabinoid which is licensed for chemotherapy-induced nausea and vomiting in the USA) shows it to be an effective antiemetic, although it is less effective than metoclopramide, and adds no benefit to 5HT3 antagonists.  Some concerns about the side effects of cannibinoids remain. 
- A multisite randomised controlled trial studying antiemetics in palliative care is underway in Australia. It will firstly test whether prescribing according to clinical guidelines based on the presumed mechanism of nausea is effective, and secondly for patients with refractory nausea, will compare methotrimeprazine (levomepromazine) with either ondansetron or best supportive care using other antiemetics.
- The potential role of octreotide in bowel obstruction is currently being studied in a multisite randomised controlled trial.