13.2 - Drugs affecting Gut motility Flashcards Preview

ESA 5 - Pharmacology > 13.2 - Drugs affecting Gut motility > Flashcards

Flashcards in 13.2 - Drugs affecting Gut motility Deck (15)
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What 3 ways is gastric motility controlled by?

myogenic - rhythmic contraction of smooth muscle cells by pacemaker cells
neural - enteric plexus
hormonal - cck, gastrin, secretin


Explain how emesis occurs

Closing of pyloric sphincter --> relaxing of cardia and esophagus --> Contraction of abdominal muscles and diaphragm


Where is the vomiting centre found?

Part of ependymal cells on the floor of the 4th ventricle


What neurotransmitters are involved in emesis control?

At Vestibular apparatus - ACh and H1
Medullar centre - ACh, H3, serotonin
Vomiting centre - Dopamine


What are the types of anti-emetic drugs? Give example types

D2 receptor antagonists - domperidone, metoclopramide
5-HT3-receptor antagonist - ondansetron
H1-receptor antagonists- cyclizine


How does domperidone work? ADRs?

Increases gastric emptying. D2 receptor antagonist
ADR - galactorrhoea, hyperprolactinemia


How dos ondensteron work? ADRs?

Reduces vagal afferent neves. 5-HT3 receptor antagonist
ADR - headaches, constipation, flushing


How does metoclopramide work? ADRs?

Blocks vagal afferents. D2 receptor antagonist
ADR - extra-pyramidal


How does cyclizine work? ADRs?

H1 receptor antagonist
ADR - prolongs QT interval


What type of laxatives are used for constipation with soft and hard faeces?

soft - use stimulant laxative
Hard - Use osmotic or bulk laxative


what are exampes of bulk laxatives? How do they work? ADR?

e.g. ispaghula. Non degradable fibre gives bulk to aid in peristalsis. Takes few days to work.
ADR - flatus,


What are examples of osmotically active laxatives? How do they work?

e.g. movicol.
Works by causing water retention in small and large bowel to increase peristalsis. Acts quickly and severely.


What are examples of stimulant laxatives? How do they work?

e.g. senna, bisacodyl
Excites sensory nerve ending, leading to water and electrolyte retention --> peristalsis. Work in 6-8 hrs.


Name an example anti-motility drug and how it works. When should it be avoided and why?

Loperamide - opiate reduce GI motility. Good for chronic diarrhoea. Avoid in IBD due to toxic megacolon


Name a bulk forming agent and how it works in diarrhoea

ispaghula. Increases water absorption by gut.