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Pharmacology > GI Drugs > Flashcards

GI Drugs Flashcards

(62 cards)

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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
Metoclopramide ADRs
Galactorrhoea | Extrapyramidal (dystonia) in 1% (contraindicated in Parkinson's)
25
Hyoscine mechanism
ACh antagonist | AKA scopolamine
26
Hysoscine uses
Motion sickness | Oral or patch
27
Hyoscine pharmacokinetics
Effects usually short lived ~2 hrs
28
Hyoscine ADRs
Systemic anti ACh Bradycardia Tolerance?
29
Cyclizine action
H1 (histamine) antagonist | Anti muscarinic effects
30
Cyclizine uses
Acute nausea | Vomiting
31
Cyclizine pharmacokinetics
Route can be oral, IV or IM | Crosses BBB
32
Cyclizine ADRs
Sedative effect
33
Cannabinoids GI use
Antiemetics
34
Benzodiazepines GI use
Antiemetic
35
Constipation non-pharmacological recommendations
Increased fibre Increased fluid Increased exercise
36
Bulk laxatives
``` 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
Bulk laxatives ADRs
Flatulence
38
Bulk laxatives contraindications
Ulceration and adhesion - could cause obstruction
39
Faecal softeners
Safe | Not always effective indicated as bulk laxatives are, but also ok in adhesions, fissures, haemorrhoids etc.
40
Osmotically active laxatives
Magnesium and sodium salts
41
Osmotically active laxatives mechanisms
Cause water retention in large bowel to increase peristalsis. Magnesium and sodium salts
42
Osmotically active laxatives pharmacokinetics
Act quickly and are severe | Usually PR
43
Osmotically active laxatives uses
Reserve for resistant constipation where urgent relief is required
44
Lactulose mechanism
Disaccharide of fructose and galactose Can't be hydrolysed by digestive enzymes Fermented in colon to produce acetate and lactate Osmotic effect
45
Lactulose pharmacokinetics
Takes 48 hrs to work | Oral
46
Lactulose uses
Used in liver failure as ammonia production is reduced
47
Macrogols
Powder given orally with fluid | Movicols, polythene glycol
48
Macrogols uses
May prevent dehydration | Initial effects within hours, but 2-4 days til full relief
49
Macrogols issues
Caution required to prevent intestinal obstruction
50
Irritant/stimulant laxatives pharmacokinetics
Rapid treatment | 6-8 hrs PO, so usually taken before bed time
51
Irritant/stimulant laxatives mechanism
Excitation of sensory nerve endings leads to water and electrolyte retention, so peristalsis
52
Bisacodyl
Irritant/stimulant laxatives
53
Antraquinones
Irritant/stimulant laxatives | Danthron, Senna, rhubarb
54
Anti motility drugs
``` Opiates Opiate analogues (Imodium/loperamide) - more potent but no CNS penetration ```
55
Anti motility drugs mechanism
Act via opioid receptors in the bowel Reduce motility - more time for fluid to reabsorb Increase anal tone
56
Anti motility drugs uses
Chronic diarrhoea | Avoid in IBD- toxic mega colon
57
Bulk forming in diarrhoea
Good in IBS and ileostomy Ispaghula etc Act via water absorption
58
Fluid adsorbents
Stools more formed | Very little use
59
Cholestyramine
Bile acid sequesterant used for bile salt induced diarrhoea
60
IBS diarrhoea
Mebeverine good Direct effect on colonic hypermobility No systemic anti muscarinic side effects Useful combined with bulk forming agents
61
Cholestyramine DDIs
Binding prevents warfarin and digoxin absorption

Pharmacology (20 decks)

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