Anti-Emetics Flashcards
1
Q
What stimulates Nausea and vomiting?
A
- Toxins: Bacterial poisons, alcohol (15%)
- Smells
- Motion sickness
- Migraine
- Pregnancy
- Drugs
2
Q
What is the physiological response of Vomiting and Nausea?
A
- Discomfort, dry mouh, salivary inhibition
- Yawning-sympathetic distress
- Reappearence of saliva
- Pylorus closes
- Tone of stomach increase
- Deep breath
- Contraction of abdominal muscle to force out food
- Forced expiration to prev inhalation
3
Q
What NT are involved in Nausea and vomiting?
A
- Histamine
- Acetylcholine
- Dopamine
- 5-HT
- Neurokinin
- Blocking these receptors in the brain prevents nausea and vomiting
4
Q
What is the vomit centre of the brain?
A
- Located within medulla
- Recieves afferent signals from vagus nerve and CTZ
5
Q
What receptors are important for vomiting?
A
- 3 receptors abundant in the chemoreceptor trigger zone (CTZ)
- BLocking these is important for prev vomiting
- D2
- 5-HT3
- NK-1
6
Q
What are the 4 main pathways?
A
- Chemoreceptor trigger zone (CTZ)
- Vagal afferent nerve fibres from GIT
- Central vestibular nuclei
- Higher centres of brain
7
Q
What is the chemoreceptor zone(CTZ)?
A
- Outside BBB
- REceptors 5-HT3, D2 and NK1 (substance P)
8
Q
What is motion sickness?
A
- Afferents from inner ear (vestibulo-cochlear system) feed into vomiting centre
- Mediated by acetlycholine and histamine
- Inner ear infections can also cause motion sickness
9
Q
How does chemotherapy induce nausea?
A
- Some chemotherapy agents stimulate release of 5-HT from enterochromaffin cells in GIT
10
Q
What are Histamine H1 receptor antagonists work?
A
- Motion sickness
- Morning sickness of pregnancy
- Space motion sickness
- Anti-muscarininc actions
- Produce drowsiness and sedation
(Block receptor in Vestibular nuclei see PP)
11
Q
What are Muscarinic M1 receptor antagonists?
A
- Prophylaxis and treatment of motion sickness
- Also reduce gastic motility
- Anti-muscarinic side effects
- Produce drowsiness
- Naturally occuring foundin Atropa belladona
- Block receptor in Vestibular nuclei (See pp)
12
Q
What is the Reflex mechanism of vomiting?
A
- Central regulation of vomiting occurs in the vomiting cntre and the CTZ
(CTZ sensitive to chemical stimuli–main site of anti-emetics) - Output from CTZ stimulates the vomiting centre, leading to initiation of vomitin
- Neuronal signals from GI tract feed into CTZ and vomiting centre
13
Q
What is the Vomiting protective reflex?
A
- Chemoreceptors in GIT activated by toxins–
- effect vagal nerves–
- feed into nucleus tractus solitarius and in turn, vomiting centre
14
Q
What are Dopamine D2 receptor antagonists?
A
- Act in CTZ but has unwanted CNS effects
- D2 receptor inv in movt
- Antagonism leads to parkinson’s like symptoms
- Effective against chemotherapy-induced emesis
- Also stimulates gastric emptying and reduce nausea
- Works in CTZ on D2 receptor
15
Q
What are 5-HT receptor antagonists?
A
- Blocks 5-HT at 5-HT3 receptors in gut and CNS
- Particularly effective against chemotherapy-induced emesis
- Not effective for motion sickness
- Work in GIT and CTZ (See pp)
