Drugs of the GI tract

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Define vomiting
The forceful contraction of gastric contents from the stomach which can be life-saving or an unwanted side effect
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Name and describe the 4 main stimuli for vomiting
Sensory: pain, repulsive smell, sight. Motion sickness: ear stimulus. Chemical: chemotherapeutic drug. Stimulus from stomach or pharynx.
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Name the 2 brain centres that process vomiting
Chemoreceptor trigger zone and nucleus solitarius
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Name the 5 receptors which are responsible for signal transmission
Dopamine-2, serotonin-3, neurokinin-1, muscarinic acetylcholine and histamine-1
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What is the role of the vomiting centre?
Sends electrical signals to the brainstem to control the relevant smooth and skeletal muscle
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Which receptors is involved in the output in the vomiting centre?
Muscarinic acetylcholine receptor
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What is the role of anti-emetics?
Drugs which block the output (vomiting centre) but input (stimulus) remains
7 of 49
Name 3 drugs which are D2 receptor antagonists, what is the stimulus?
Phenothiazines( chemical and radiation induced), Domperidone, Metoclopramide
8 of 49
Name a drug that is a 5HT3 receptor antagonist, what is the stimulus?
Ondansetron: chemical and radiation induced
9 of 49
Name a drug and stimulus that is a muscarinic cholinergic receptor antagonist
Hyoscine: motion sickness and stomach irritation
10 of 49
Name a drug and stimulus that is a H2 receptor antagonist
Cyclizine: motion sickness
11 of 49
Name a drug and stimulus that is a neurokinin-1 receptor antagonist.
Aprepitant: chemotherapeutic drug
12 of 49
There is a balance between peristalsis and water movement of the gut for faecal formation, explain it.
Constipation: increase in water absorption and decrease in peristalsis. Diarrhoea: decreased in water absorption and increase in peristalsis
13 of 49
Name 3 factors that affect peristalsis
Neurohumoural mechanisms, pathogens and drugs
14 of 49
Define diarrhoea
The frequent passage of liquid faeces
15 of 49
Name 4 factors that can aggravate diarrhoea
Drugs, anxiety, toxins, pathogens
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What are the 3 approaches to treating diarrhoea?
Treat fluid and electrolyte balance first, then use an anti-infectious agent, lastly use an anti-motility agent.
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If diarrhoea is caused by a pathogen, why is an anti-motility drug not advised?
Because the body is trying to get rid of the pathogen.
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Name 2 classes of anti-motility drugs
Opiates and adsorbents
19 of 49
Loperamide, codeine, diphenoxylates: which class of drugs do they belong to?
opiates
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What is their mechanism of action?
Increase tone but decrease propulsive activity, contracting the pyloric, ilio-caecal and anal sphincters
21 of 49
Name 3 adsorbents and how do they work?
Kaolin, chalk and pectin: absorb toxic molecules onto its surface
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Name the 2 types of drugs used to treat constipation
Laxatives/purgatives and drugs which increase GI tract motility
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How do the drugs of constipation work?
Laxatives/purgatives: alter the rate of fluid absorption and secretion. Drugs which alter GI tract motility: increase contraction of smooth muscles.
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Name the 4 types of laxative/purgative drugs
Bulk laxatives, osmotic laxatives, faecal softeners and stimulant purgatives
25 of 49
With named examples, how do bulk laxatives work?
Bran, methyl cellulose: they bulk up food and absorb water to make bolus softer
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With named examples, how do osmotic laxatives work?
Lactulose, macrogols: movement of water from blood vessels to gut lumen
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With a named example, how do faecal softeners work?
Docusate sodium: break down of components of faeces
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With named examples, how do stimulant purgatives work?
Senna, bisacodyl: stimulate peristalsis soft smooth muscle in gut
29 of 49
Explain the MOA of domperidone
Increase lower oesophageal spinster pressure, increase gastric emptying and increase duodenal peristalsis
30 of 49
Explain the MOA of Metoclopramide
Accelerates gastric emptying
31 of 49
Describe the role of bile and journey of bile.
It dissolves lipids, synthesised in the liver but transported to the gall bladder for to actively release it via the cystic duct and emptying into the second part of the duodenum (ampulla of Vater).
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What is cholestasis?
When flow of bile is blocked due to chlolesterol build-up in the common bile duct
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Are water and electrolytes a content of the bile?
No
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What are the components of the bile in order from highest to lowest concentration?
Bile salts, cholesterol and phospholipids
35 of 49
Describe gall stones
They are pebble-like cholesterol due to high levels of cholesterol in the bile, when the gall bladder contracts, they cause extreme pain
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Who is at most risk of gall stones
Caucasian, females, obese, 40+ years of age
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What are the symptoms of gall stones?
Rapidly increasing pain lasting from 30 mins to hours in upper right quadrant of abdomen, between scapula, under right shoulder joint and biliary spasms
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What is the surgical procedure to remove gall stones
Cholecystectomy using keyhole surgery, if cholesterol blocks common bile duct then remove suing ERCP
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What is the non-surgical method of removing gall stones?
Oral dissolution therapy: ursodiol is natural bile salt that dissolves gall stone, prevents uptake of cholesterol by the GI tract and increases bile flo
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Name 5 drugs to treat biliary spasms
Morphine buprenophine, pethidine, atropine or nitrates
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How does morphine work, what is a disadvantage of it?
Relieves pain but build pressure in sphincter of Oddi causing more pain
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How does buprenophine work?
Same as morphine
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Which drug is most commonly used?
Pethidine
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What is the advantage of using atropine?
Can he used alongside pain relief medication
45 of 49
How do nitrates treat biliary spams?
They relieve pressure in the bile system
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What is cholecystitis?
Inflammation of gall bladder due to an infectious agent
47 of 49
Name 4 symptoms of cholecystitis
Extreme pain, nausea, vomiting and inflammation
48 of 49
Name the 3 steps to treat cholecystitis
Antibiotics then surgery to remove gall bladder, pain relief medication then IV fluids to replace those lost through vomiting
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Other cards in this set

Card 2

Front

Name and describe the 4 main stimuli for vomiting

Back

Sensory: pain, repulsive smell, sight. Motion sickness: ear stimulus. Chemical: chemotherapeutic drug. Stimulus from stomach or pharynx.

Card 3

Front

Name the 2 brain centres that process vomiting

Back

Preview of the front of card 3

Card 4

Front

Name the 5 receptors which are responsible for signal transmission

Back

Preview of the front of card 4

Card 5

Front

What is the role of the vomiting centre?

Back

Preview of the front of card 5
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