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Biomedical Pharmacology > Lecture 10 -Gastrointestinal > Flashcards

Lecture 10 -Gastrointestinal Flashcards

1
Q

What are the control of gastric acid secretion?

A

Vagus: sight, smell, taste Release of gastric: presence of food (protein) Histamine CCK GIP Somatostatin

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2
Q

What is the PH in the stomach controlled by?

A

Gastric acid secretion

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3
Q

Why is secretion of HCL needed?

A

To get a low PH to get activation of relevant stomach enzymes (e.g. pepsin)

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4
Q

Why is carbonic anhydrase needed?

A

Generation of free H+ ions

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5
Q

What are the forms gastric secretion can take?

A

HCL Pepsinogen Mucus Bicarbonate ions

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6
Q

What is the acidic environment in the stomach maintained by?

A

Action of parietal cells

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7
Q

What do parietal cells do?

A

Secrete H+ against concentration gradient

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8
Q

Where does ATPase get hydrogen ions from?

A

Carbon dioxide and water

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9
Q

What are the bicarbonate ions exchanged for?

A

Chloride ions, the chloride ions will be transported along with K+ into gut lumen via a symporter mechanisms

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10
Q

When do peptic ulcers arise?

A

When the protective layer is disrupted Elevated prolonged acidity in the gut

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11
Q

What are the causes of peptic ulcer?

A

Stress: activation of vagus nerve NSAIDs: e.g. aspirin Diet: disrupt gut favouring breakdown and degradation of cell types within cell wall Alcohol Zollinger-Ellison Syndrome: tumour of cells tjat product gastric leading to altered HCL Bacterial: helicobacter

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12
Q

What may Helicobacter pylori be involved in?

A

Pathology of peptic ulcer

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13
Q

Why was it difficult to establish cultures?

A

Gut helicobacter pylori takes longer period to be established in the gut

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14
Q

What does G cell create?

A

Gastrin

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15
Q

What does gastrin interact with?

A

Cholecystokinin receptors to promote the release of local hormone histamine

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16
Q

What does histamine act upon?

A

Histamin receptor (H2) that stimulate the production of pumping of H+ ions in the target cell (parietal cells)

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17
Q

What does somatostatin regulate?

A

H+ ion level at many different sites at 3 different cell types

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18
Q

How may you be prone to stress ulcers?

A

Activation of the parasympathetic nerve system and the vagus nerve Elevation of ACH -> activate muscarinic receptors and cause reduction in HCL

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19
Q

What does prostaglandin receptor have negative effect on?

A

Histamine release

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20
Q

What is Aspirin mode of action?

A

Inhibit the enzyme that concert arachidonic acid into prostaglandin Inhibit enzyme: cyclooxygenase

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21
Q

What is Aspirin involved in?

A

Inflammatory pathways

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22
Q

What happens in the presence of Aspirin?

A

Prolonged and elevated secretions of H+ and formation of HCL in the gut which can lead/contribute to peptic ulcer

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23
Q

How can Aspirin contribute to peptic ulcer?

A

Manipulation of gastrin, enterochrokaffin-like, parietal cell axis

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24
Q

What are Antacids?

A

Medicines that counteract (neutralise) the acid in your stomach to relieve indigestion and heartburn

25
Q

Antacids

A

Buffer/neutralise acid, raise PH Promote healing over time Magnesium and Aluminium salt Sodium bicarbonate Alginates, simeticone (affect viscosity of mucus)

26
Q

What is magnesium salt produce?

A

Diarrhoea

27
Q

What does aluminium salt produce?

A

constipation

28
Q

Histamine H2 receptor antagonist

A

Histamine receptor subtypes identified in the early 1970s

29
Q

What is the effect of Histamine H2 receptor antagonists?

A

Basal and stimulated acid and pepsinogen secretion Promote healing Ulcer relapse

30
Q

Proton pump inhibitors

A

Irreversible inhibitors of H+/K+ ATPase Produces fastest rate of healing

31
Q

What are advantages of proton pump inhibitors ?

A

Better tolerated and cheaper than other drugs

32
Q

What is the action range of proton pump inhibitors?

A

Long term action: 2-3 days Maximum effectiveness: 5 days

33
Q

What are proton pump inhibitors associated with?

A

Increased risk of infection Pneumonia and C.difficile

34
Q

Where are proton pump inhibitors administered ?

A

Enteric coating

35
Q

What can happen to drug at low PH?

A

Drug can be easily and rapidly broken down

36
Q

H.pylori Therapy

A

Present in peptic ulcers Healing of peptic ulcers (80% vs 20% re-occurrence when eradicated)

37
Q

Where are Bismuth chelate used in?

A

resistant cases

38
Q

Bismuth Chelate

A

Toxic to H.pylori and prevent adherence Coat ulcer base, adsorb pepsin, stimulate PG synthesis and bicarbonate secretion Minimally absorbed and normally fully excreted

39
Q

Sucralfate

A

Aluminium hydroxide and sulfated sucrose Form complex gels with mucus, Inhibit pepsin, stimulate secretion of mucus, PGs and bicarbonate Requires acidic environment and block absorption of some other drugs May cause constipation

40
Q

What is misoprostol?

A

Prostaglandin E1 analogue

41
Q

What is a drawback of Bismuth Chelate?

A

Form a paste than can form obstruction within gut

42
Q

What can control of emesis be?

A

central or local

43
Q

What does the reflex of vomiting bring?

A

Contraction of the gut

44
Q

What does CNS component give rise to?

A

Vomiting or nausea feeling

45
Q

Centrally mediated vomiting reflexes

A

Stimulation of vomiting centre via the CTZ or chemoreceptors trigger in Medulla of brain

46
Q

How can the antiemetic effect be generated?

A

Interference with the function of the CTZ or vomiting centre

47
Q

Motion sickness

A

Disturbance within labyrinth in the ears in the vestibular system

48
Q

What can be found in the vestibular nucleus?

A

Histamine receptor (H1) Antagonist Mach antagonist

49
Q

What can be used to treat nausea?

A

5HT3 antagonist

50
Q

H1 receptor antagonist

A

Effective against motion sickness Morning sickness in pregnancy

51
Q

What are the side effects of H1 receptor antagonist ?

A

Drowsiness sedation

52
Q

Muscarinic Antagonist

A

Block muscarinic receptor common motion sickness prophylactic

53
Q

What are the side effects of muscarinic antagonist?

A

Dry mouth Blurred vision Less drowsiness than antihistamine

54
Q

What are the side effects of selective 5-HT3 receptor antagonist?

A

GI effects and headaches

55
Q

What are the frequent side effects of Antipsychotics?

A

Drowsiness Hypotension Motor disorders

56
Q

What are Benzodiazepine?

A

Adjunct Therapy In circumstances where Anxiety is a factor

57
Q

D2 receptor antagonist

A

Increase GI motility - used for other GI conditions

58
Q

What can metoclopramide have?

A

Serious CNS side effects

59
Q

What is Neurokinin-1 antagonist ?

A

Aprepitant inhibiting the action of substance P; inhibitor of P450

Biomedical Pharmacology (19 decks)

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