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Pharmacology > GI Drugs > Flashcards

GI Drugs Flashcards

1
Q

Where is acid produced from?

A

The parietal cells in the body of the stomach

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2
Q

What are the parietal cells of the stomach stimulated by?

A

Parasympathetic from the vagus nerve release Ach acting on parietal cells.
Enterochromaffin like Cell releases histamine which acts on H2 receptors
Gastrin is released and acts on CCK receptors on the parietal cells.

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3
Q

How is gastrin released?

A

So gastrin is released by G cells, these G cells are stimulated by peptides/ amino acids in the stomach lumen and stimulated by vagaries innervation- Ach and GRP.

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4
Q

What is the alkaline tide?

A

I when we pump a lot of cid into our stomach, we have a corresponding alkaline rush into the blood- this is called the alkaline tide.

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5
Q

How is acid secretion in the stomach inhibited normally?

A

When food leaves the stomach the pH will drop (get more acidic) this causes D cells to be stimulated which release somatostatin, somatostatin then acts and blocks G cells (which produce gastrin) and ECL cells (which produce histamine).

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6
Q

As the stomach is designed to digest biological material, it can easily digest itself, what is in place to protect it?

A

Athe stomach has many defences in place…
Has mucus/HCO3- which are released by surface mucous cells and neck cells in gastric glands
It forms a thick alkaline viscous layer which adheres to the epithelium.
The epithelial surface is kept at a higher pH.
Prostaglandins which increase blood flow
Growth factors
Mucosal blood flow

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7
Q

Give some things which can breach the stomach defences…

A

Alcoh (dissolves the mucus layer), smoking NSAIDS (inhibit prostaglandin), H pylori

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8
Q

Why might you give someone aluminium hydroxide?

A

Aluminium hydroxide is an antacid, it is given to someone experiencing heartburn and acid indigestion.

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9
Q

How does aluminium hydroxide work?

A

It acts by neutralising HCL in gastric secretions, aluminium hydroxide is slowly solubilised in the stomach and reacts with HCL to form aluminium chloride and water.

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10
Q

What could you give to someone suffering from IBS, give the MOA and the side effects…

A

Hyoscine hydrobromkde, it is an anti spasmodic muscarinic receptor antagonist, it relaxes the intestinal smooth muscles by antagonising the muscarinic receptors (M2 and M3) can be transdermal or oral.

For all antimuscarinics you get: constipation, dizziness, dry mouth, headache, nausea, palpitations, tachycardia, skin reaction, urinary disorders.

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11
Q

What is ranitidine?

A

It is a histamine (H2) agntagonist, remember histamine which is released from ECL cells binds to and stimulates parietal cells

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12
Q

How could you treat someone with peptic ulcers, chronic dyspepsia, GORD, reflux, oesophagitis??

A

You could use histamine (H2) antagonists like Ranitidine

Or proton pump inhibitors like Esomeprazole

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13
Q

What is the mechanism of action of ranitidine, and give its side effects…

A

It blocks the H2 receptors on the parietal cells in the stomach, it reduces the amount of acid produced

You get constipation, diarrhoea, dizziness, fatigue, headache, myalgia, loose stools, but has interactions and side effects which are minimal.

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14
Q

Does esomeprazole work straight away?

A

It is taken 30 mins before the meal, it has a delayed response as only destroys the active pumps, it is used for long term not immediate effect, has a max efficacy after 2-3 days, will take a few days for acid production to return to normal after.

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15
Q

What are the side effects of proton pump inhibitors?

A

Headache, diarrhoea, constipation, abdo pain, nausea and vomiting and fever.

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16
Q

What is H.pylori?

A

The bacterium which causes peptic ulcer diseas e
It infects the lower part of the stomach- the antrum
It causes inflammation of the gastric mucosa (gastritis) this is often asymptomatic
This causes a duodenal or gastric ulcer, it causes severe complications including bleeding ulcer and perforated ulcer.
It is a potential carcinogen, as it increases the risk of gastric cancer.

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17
Q

How do you treat H pylori?

A

2 antibiotics and a full acid blockage with PPI (a week at a high dose)
The 2 antibiotics used…
Amoxicillin= pre ents the cell wall synthesis
Lansoprazole= it is a PPI, it slows and prevents the production of acid with8m the stomach.
Clarithromycin= it is used in combination with other medications to eliminate the H pylori, a bacterium that causes ulcers
It prevents bacteria from multiplying and acts as a protein synthesis inhibitor and can be taken wither in a pill or liquid form.

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18
Q

What is GORD and what are the risk factors of GORD?

A

Reflux

Normally due to: increased abdominal pressure, pregnancy, alcohol, NSAIDS.

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19
Q

How might you advise someone with GORD, as their first step?

A

Stop smoking, stop drinking alcohol, don’t take NSAIDS, lose weight, avoid certain foods like coffee and alcohol, chocolate, fatty, spicy food, try to reduce stress and eat smaller more frequent meals.

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20
Q

If lifestyle doesn’t work for GORD, what would you advise?

A

Taking Antacids like aluminium hydroxide/Alginates.
Histamine receptor antagonists (ranitidine)
PPI (esomeprazole)

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21
Q

What is the treatment of oesophagitis and how would it differ it it became barrettes oesophagus, and what is Barrett’s oesophagus?

A

Oesophagitis is inflammation of the oesophagus, it depends on the degree, so if it’s mild then you need to change your lifestyle and you need a few weeks of Antacids.
May need PPI for life if you develop Barrett’s oesophagus.
Barrett’s oesophagus is where your normal epithelium (simple squamous) is changed to columnar epithelium via. metaplasia.

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22
Q

How would you treat a peptic ulcer?

A

Stop NSAIDS
H2RA/PPI for 6 weeks
H Pylori eradication (if was caused by H pylori and it’s eradicated may not need PPI formlics)

23
Q

What sort of things effect the chemoreceptor trigger zone?

A

Vestibular nuclei, sensory afferent via. The midbrain, visceral afferent from the gut, therefore we can block sickness, by blocking these paths!

24
Q

What is the first line choice for motion sickness and what is it’s mechanism of action?

A

Hyoscine hydrobromide
They are competitive blockers of muscarinic Ach receptors in both the vestibular nuclei, but also at the CTZ! These receptors are all over the body and are part of the parasympathetic nervous system.

25
Q

What side effects would you expect with motion sickness tablets like hyoscine hydrobromide?

A

Sedation
Memory problems
Glaucoma
Dry mouth and constipation

26
Q

What is a H1 receptor antagonist? Give its mechanism of action and an example….

A

It’s essentially an anti histamine, it acts on the vestibular nuclei and inhibits histaminergic signals from the vestibular system to CTZ in the medulla.

Promethazine: good for morning sickness in pregnancy.

27
Q

What would you give to someone suffering from morning sickness?

A

you would give promethazine
The side effects include: sedation, excitation, antimuscarinic so you get dry mouth, constipation, urinary retention, cardiac toxicity (long QT interval).

28
Q

How do 5HT3 receptor antagonists work? Give an example…

A

They act on the visceral afferent, serotonin normally causes smooth muscle contraction and increases gut secretions, hence regulates appetites.

By blocking receptors, it peripherally reduces GI motility and secretions.
Ondonestron.

29
Q

What are D2 receptor antagonists?

A

So these are prokinetic
Normally dopamine reduces Ach and hence prevents GI smooth muscle therefore inhibiting dopamine causing gastric emptying.

30
Q

When would you use metadopromide or domperidone?

A

They are good for GORD, paralytic lieu’s, chemo.

31
Q

What are some of the side effects which come with taking a D2 receptor antagonist?

A

So with metacloperamide you can get galactorrhoea (via. Prolactin release)
You also get extra pyramidal effects like dystopia and Parkinsonism.

With domperidone you can also get galactorrhea and more seriously, you can get sudden cardiac death.

32
Q

What is another use of domperidone, other than anti nausea effects?

A

It can improve lactation in breastfeeding mothers.

33
Q

Normally dopamine causes movement, how does this differ in terms of GI?

A

Dopamine is an important neurotransmitter which is involved in regulation of GI motility.

34
Q

If someone constantly needed to vomit in hospital, what could you consider other than drugs?

A

Nasogastric tube which can drain the stomach, preventing the need to vomit.

35
Q

For gut pathology which is causing someone to vomit, what is the gold standard drug use?
(Anti-emetics)

A 
OCD 
Ondansetron (5HT3 receptor antagonist) 
And/or 
Cyclizine (histamine receptor antagonist) 
Then add 
Dexamethasone (corticosteroid)
36
Q

When should you not be using prokinetics like metacloperamide and domperidone?

A

When there is an obstruction, as this increases risk of perforation.

37
Q

What are the ‘zines’, what are they used for and what are the side effects?

A

The zines are antipsychotics, they act on the CTZ and may block histamine and muscarinic receptors, they don’t know.
They are used in motion sickness, vertigo, prochlorperazine in pregnancy.

38
Q

What are the actions of cortisol, and hence what do you think the side effects of taking corticosteroids will be?

A

Cortisol is a stress hormone, which is released by the ZONA fascicules in the adrenal medulla, it causes the blood sugar level to rise through gluconeogenesis. It also regulates blood pressure.

Therefore side effects…
Increase in appetite
Insomnia
Increase in blood sugar

39
Q

When are corticosteroids given?

A

Peri operative nausea and vomiting
Chemotherapy (dexamethasone as it’s stronger than methylprednisolone)
Palliation
Give when someone has brain mets as it reduces inflammation and ICP.

40
Q

What is nabilone, what’s it used for and what side effects do you get?

A

It’s a cannabinol, it is assumed to act on the CTZ, it is given as a last line when someone is having chemo.
Side effects: dizziness and drowsiness

41
Q

What is hyperemesis gravidarum?

A

This is a form of severe morning sickness in pregnancy, when you get a rapid rise in Beta hCG stimulating the CTZ, typically weeks 4-16 but may continue beyond, there is a higher risk with multiple pregnancies, also get a risk of dehydration and electrolyte imbalance, urinalysis ketones.

42
Q

What drugs would you give for hyperemesis gravidarum?

A

Promethazine (h1 receptor antagonist)
Or
Prochlorpeeazine (D2 receptor antagonist)

43
Q

What is the treatment given for someone with diarrhoea and give the mechanism of action…

A

Loperamide (an opioid receptor agonist), it is specific to mu receptors in the MYENTERIC plexus, it decreases the tone of longitudinal and circular smooth muscle as well as decreasing peristalsis but increasing segmental contractions.
It increases the transit time and decreases colonic mass movement by suppressing the gastrocolic reflex.

44
Q

What are the side effects of Loperamide?

A

Loperamide (the opioid receptor agonist used to treat constipation, side effects include: paralytic ileus and nausea and vomiting.

45
Q

What is Isphaghula husk?

A

A bulk forming laxative, used for constipation, it forms a bulky and more liquid like still which are softer and easier to pass.

46
Q

What are the side effects of bulk forming laxatives?

A

Bloating, flatulence, nausea, vomiting and stomach cramping.

47
Q

What is senna used for and what is its class?

A

It is a stimulant laxative class which is used for constipation, it directly stimulates the myenteric plexus increasing peristalsis, it may be given orally or per rectum.

48
Q

What is lactulose?

A

An osmotic laxative it increases the amount of water in the large bowel by drawing fluid In.

49
Q

How long would you give senna for and would you give if there was an obstruction?

A

You would use for less than 1 week normally

Don’t give if there is an obstruction, because just means more movement against the obstruction.

50
Q

What are the side effects of senna?

A

Abdominal cramping
Diarrhoea
NV
Burping

51
Q

Why is lactulose useful for use in children?

A

Can mix in with food.

52
Q

What is movicol, explain how it works…

A

Movicol isa macrogol, it increases the amount of water in the large bowel and retains the fluid they came with.

53
Q

What are the side effects of Movicol?

A

Electrolyte imbalance.
Nausea, vomiting
Flatulence.

54
Q

What is glycerin suppository?

A

A stool softener, it decreases the surface tension of the stool and increases the penetration of fluid into the stool.

Pharmacology (15 decks)

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