Causes of nausea and vomiting
Nausea and vomiting are symptoms of several conditions, including, gastrointestinal disorders, dysmobility (slowing down of food through the GI tract), food poisoning, migraine, chemotherapy and radiotherapy for cancer treatment, reaction to surgical anaesthetic.
The vomiting reflex originates in the chemoreceptor trigger zone (CTZ) of the area postrema of the brain. The CTZ is triggered by nerve messages sent from the small intestines stimulated by the neurotransmitters dopamine or serotonin. When triggered the CTZ sends nerve messages to the vomiting centre of the brain, causing nausea and vomiting.
Medications for nausea and vomiting
Medications used to relieve nausea and vomiting include two types of antiemetic:
- Serotonin receptor-antagonists like ondansetron work by binding to specific 5HT3 receptors in the intestine and in the CTZ and block the transmission of nerve messages from the intestines and from the CTZ to the vomiting centre in the brain, which prevents the vomiting reflex from being triggered.
- Dopamine antagonist like domperidone and metoclopramide work by binding to dopamine receptors in the CTZ blocking the transmission of nerve messages to vomiting centre in the brain, which prevents the vomiting reflex from being triggered. They also have gastrokinetic action by interacting with nervous control of muscle contraction in the stomach and upper intestine, which helps relieve symptoms of dysmobility and this also helps prevent vomiting.