Medication Corner

Ondansetron is an anti-emetic that was developed to prevent and treat nausea and vomiting that is induced by cytotoxic chemotherapy and radiotherapy. It is also indicated for post-operative nausea and vomiting, however it is not usually an anti-emetic of choice in palliative care. 

Ondansetron works by blocking serotonin, a neurotransmitter that can trigger nausea and vomiting, specifically in the gastrointestinal tract and the brain. 

Common side effects include constipation, flushing and headache. Opioid use is common in palliative care and when ondansetron is used in conjunction with opioids, constipation can be a significant problem.  

There are some risks associated with QT prolongation and serotonin syndrome, particularly when used with other medications with similar effects. Ondansetron should not be used in conjunction with apomorphine, a medication that treats certain episodes of Parkinson's Disease that affect movement. 

Ondansetron is mostly used in tablet form or disintegrating tablet (wafer). The wafer is placed on top of tongue, allowed to disperse, and then swallowed. 

Subcutaneous injection is possible, but is not often used due to risk of local adverse effects on soft tissues. 

Ondansetron can be a good choice of anti-emetic for patients with renal failure, and can also be considered for refractory itch when other approaches have not shown benefit.  

Information from Palliative Care Handbook and NZ formulary 

Links:

New Zealand Formulary https://nzf.org.nz/

Palliative Care Handbook: https://www.hospice.org.nz/palliative_care_handbook