Flashcards in 13.2 - Drugs affecting Gut motility Deck (15):
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?
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