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Pharmacology > GI Drugs > Flashcards

GI Drugs Flashcards

0
Q

PPI pharmacokinetics

A

Acid activated pro drugs
Can only bind to open channels so take a few meals to take effect
Max efficacy after 2-3 days

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1
Q

PPI mechanism

A

Act on the H/K ATPase on parietal cells

Covalently bind to cysteines

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2
Q

Omeprazole
Lansoprazole
Rabeprazole

A

PPIs

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3
Q

PPI ADRs

A

Can alter CYP450 activity

Diarrhoea due to pH changes

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4
Q

H2 antagonist pharmacokinetics

A

Short half life, so twice daily

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5
Q

H2 antagonist mechanism

A

Prevent histamine mediated amplification of acid production

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6
Q

Cimetidine

A

H2 antagonist
Affects CYP450
Diarrhoea
Gynaecomastia

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7
Q

Ranitidine
Nizatidine
Famotidine

A

H2 antagonists

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8
Q

Alginates mechanism

A

Raft action
No known side effects
Not much evidence in large trials

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9
Q

Sucralfate

A

Alginate

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10
Q

Antacids mechanism

A

Buffer solution

No known side effects (aluminium may cause dementia?)

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11
Q

Rennies, Gaviscon

A

Antacids

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12
Q

Guidelines for peptic ulcer

A

Stop NSAIDs
H2 antagonist or PPI
Eradicate H Pylori using a penicillin derivative and clarithromycin

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13
Q

Domperidone uses

A

Anti emetic in acute nausea and vomiting, particularly if caused by L dopa or dopamine agonists
Stimulate milk production (breastfeeding)

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14
Q

Domperidone mechanism

A

D2 dopamine receptor antagonist
Acts on postrema on the floor of the 4th ventricle
Acts on the stomach to increase the rate of gastric emptying

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15
Q

Domperidone pharmacokinetics

A

Oral or PR
Extensive first pass metabolism
Doesn’t cross BBB

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16
Q

Domperidone ADRs

A

Prolactin release causes galactorrhoea

Rarely dystonia

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17
Q

Ondansteron mechanism

A

5HT-3 antagonist
5HT release into the gut causes vagal stimulation
Acts on postrema on the floor of the 4th ventricle
Acts against vagal afferent nerves in the GI system

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18
Q

Ondansteron indications

A

Radiation/chemo/post op sickness

Effect enhanced by a single dose of a corticosteroid

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19
Q

Ondansteron route

A

IV
IM
Oral

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20
Q

Ondansteron ADRs

A

Headaches
Constipation
Flushing

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21
Q

Metoclopramide action

A

D2 antagonism
Anticholinergic (GI)
Blocks vagal afferent 5HT-3 (GI)

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22
Q

Metoclopramide uses

A

GI cause
Migraine
Post op

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23
Q

Metoclopramide pharmacokinetics

A

Routes - oral, IV, IM

T 1/2 ~ 4 hrs

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24
Q

Metoclopramide ADRs

A

Galactorrhoea

Extrapyramidal (dystonia) in 1% (contraindicated in Parkinson’s)

25
Q

Hyoscine mechanism

A

ACh antagonist

AKA scopolamine

26
Q

Hysoscine uses

A

Motion sickness

Oral or patch

27
Q

Hyoscine pharmacokinetics

A

Effects usually short lived ~2 hrs

28
Q

Hyoscine ADRs

A

Systemic anti ACh
Bradycardia
Tolerance?

29
Q

Cyclizine action

A

H1 (histamine) antagonist

Anti muscarinic effects

30
Q

Cyclizine uses

A

Acute nausea

Vomiting

31
Q

Cyclizine pharmacokinetics

A

Route can be oral, IV or IM

Crosses BBB

32
Q

Cyclizine ADRs

A

Sedative effect

33
Q

Cannabinoids GI use

A

Antiemetics

34
Q

Benzodiazepines GI use

A

Antiemetic

35
Q

Constipation non-pharmacological recommendations

A

Increased fibre
Increased fluid
Increased exercise

36
Q

Bulk laxatives

A 
Insoluble, non-absorbable substances which distend the gut 
Eg ispaghula 
Vegetable fibre-resistant to digestion 
Take a few days to work
Normal fluid intake essential
37
Q

Bulk laxatives ADRs

A

Flatulence

38
Q

Bulk laxatives contraindications

A

Ulceration and adhesion - could cause obstruction

39
Q

Faecal softeners

A

Safe

Not always effective indicated as bulk laxatives are, but also ok in adhesions, fissures, haemorrhoids etc.

40
Q

Osmotically active laxatives

A

Magnesium and sodium salts

41
Q

Osmotically active laxatives mechanisms

A

Cause water retention in large bowel to increase peristalsis.
Magnesium and sodium salts

42
Q

Osmotically active laxatives pharmacokinetics

A

Act quickly and are severe

Usually PR

43
Q

Osmotically active laxatives uses

A

Reserve for resistant constipation where urgent relief is required

44
Q

Lactulose mechanism

A

Disaccharide of fructose and galactose
Can’t be hydrolysed by digestive enzymes
Fermented in colon to produce acetate and lactate
Osmotic effect

45
Q

Lactulose pharmacokinetics

A

Takes 48 hrs to work

Oral

46
Q

Lactulose uses

A

Used in liver failure as ammonia production is reduced

47
Q

Macrogols

A

Powder given orally with fluid

Movicols, polythene glycol

48
Q

Macrogols uses

A

May prevent dehydration

Initial effects within hours, but 2-4 days til full relief

49
Q

Macrogols issues

A

Caution required to prevent intestinal obstruction

50
Q

Irritant/stimulant laxatives pharmacokinetics

A

Rapid treatment

6-8 hrs PO, so usually taken before bed time

51
Q

Irritant/stimulant laxatives mechanism

A

Excitation of sensory nerve endings leads to water and electrolyte retention, so peristalsis

52
Q

Bisacodyl

A

Irritant/stimulant laxatives

53
Q

Antraquinones

A

Irritant/stimulant laxatives

Danthron, Senna, rhubarb

54
Q

Anti motility drugs

A 
Opiates
Opiate analogues (Imodium/loperamide) - more potent but no CNS penetration
55
Q

Anti motility drugs mechanism

A

Act via opioid receptors in the bowel
Reduce motility - more time for fluid to reabsorb
Increase anal tone

56
Q

Anti motility drugs uses

A

Chronic diarrhoea

Avoid in IBD- toxic mega colon

57
Q

Bulk forming in diarrhoea

A

Good in IBS and ileostomy
Ispaghula etc
Act via water absorption

58
Q

Fluid adsorbents

A

Stools more formed

Very little use

59
Q

Cholestyramine

A

Bile acid sequesterant used for bile salt induced diarrhoea

60
Q

IBS diarrhoea

A

Mebeverine good
Direct effect on colonic hypermobility
No systemic anti muscarinic side effects
Useful combined with bulk forming agents

61
Q

Cholestyramine DDIs

A

Binding prevents warfarin and digoxin absorption

Pharmacology (20 decks)

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