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mhunger
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Vomiting (AKA emesis)
- protective mechanism in reponse to some trigger such as:
- irritants
- infection
- distention
- blockage
- motion sickness
- umpleasant sight or smell
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Sympathetic responses to nausea
- increased respiration
- dilation of pupils
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Parasympathetic responses to nausea
- profuse salivation
- pronounced motility of the esophagus, stomach and duodenum
- relaxation of the esophageal sphincter
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The process of vomiting
- person takes a deep breath
- pylorus closes
- glottis closes so respiration stops
- stomach is squeezed between the diaphragm and abdominal muscles, causing rapid emptying
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Neurotransmitters involved in nausea and vomiting
- H1 (histamine1) receptors
- M1 (muscarinic1) receptors
- D2 (dopamine2) receptors
- serotonin (5-hydroxytryptamine3 5_ht3) receptors
- NK1 (neurokinin1) receptors
- CB1 (cannabinoid1) receptors
- antagonists for all of these used for treatments
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H1 receptor antagonists
antiemetic and antispasmodic activity by blocking H1 receptors
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M1 (Muscarinic 1) receptor antagonists
- work by correcting the imbalance of acetylcholine and norepinephrine that can occur in motion sickness
- block signals to the brain that cause nausea and vomiting
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D2 (Dopamine 2) receptor antagonists
- not used as an antipsychotic therapy
- block D2 receptors in the chemoreceptor trigger zone (CTZ)
- effects are similar to both H1 and M1 receptor antagonists
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5-HT3 (Serotonin) receptor antagonists
prevent nausea/vomiting due to cancer chemotherapy or surgery by blocking 5-HT3 receptors in CTZ
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NK1 (Neurokinin1) receptor antagonists
used to prevent and treat acute and delayed nausea and vomiting associated with chemotherapy
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CB1 (Cannabinoid1) receptor antagonists
antiemetic action of CB1 receptor agonists is due to stimulation of CB1 receptors in the vomiting center
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Adjunct therapies used in combination with antiemetics
- benzodiazepines (prevent nausea and vomiting associated with chemo)
- glucocorticosteroids (augment antiemetic effect of %-HT3 receptor antagonist during chemo)
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Benzquinamide
antagonizes both muscarinic and H1 receptors in CTZ to decrease vomiting center activity
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Diphenidol
controls dizziness, nausea and vomiting associated with Meniere's disease, ear surgery and ear disorders
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Trimethobenzamide
may inhibit CTZ where emetic impulses are sent to the vomiting center
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