Causes of nausea and vomiting

 

 

Opioid induced

 

Drugs such as opioids may cause nauseousness and vomiting via three ways;

 

1. Stimulation of the chemoreceptor trigger zone (CTZ)

2. Inhibition of gut motility

3. Stimulation of the vestibular apparatus

 

 Opioids stimulate the mu and delta receptors on the CTZ  which subsequently activates the  D2 (dopamine type 2 receptor), 5-HT3 receptor or NK-1 receptors present on the vomiting centre. Once the vomiting centre is stimulated, impulses are sent to the somatic and visceral receptors i.e abdominal muscles and vomiting occurs.

 

In the gastrointestinal tract, opioids can act on the mu receptors which inhibit gut motility and decreases peristalsis. This change of activity is detected by mechanoreceptors and information is relayed via the serotonergic pathway to the vomiting centre.  Furthermore, opioids increase the sensitivity of the vestibular apparatus located in the temporal region of the brain. The increased activity may result in dizziness and impulse is relayed via the serotonergic and histamine pathway to the VC.

 

Other drugs such as NSAIDs, antibiotics and iron supplements may irriatate the lining of the GI tract. This triggers the activation of mucosal receptors which stimulates the VC.