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PHARMACOLOGY Flashcards

1
Q

mechanism of PPIs

A

irreversible inhibition by covalent modification of the gastric gland parietal cell H+/K+ ATPase present in the apical membrane

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2
Q

where are PPIs activated?

A

in the acidic environment of the canaliculus

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3
Q

indications for PPIs

A
  1. peptic ulcer disease (prevention and treatment)
  2. dyspepsia and GORD (symptomatic relief)
  3. eradication of H pylori
  4. Zollinger-Ellison syndrome
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4
Q

give examples of PPIs

A

omeprazole

lansoprazole

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5
Q

adverse effects of PPIs

A
  • diarrhoea
  • headache
  • abdominal pain
  • fatigue
  • dizziness
    ? increased risk of C diff
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6
Q

what might prolonged therapy with a PPI result in?

A

rebound acid hyper secretion upon discontinuation

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7
Q

risk associated with long term therapy using PPIs in the elderly

A

increased risk of bone fracture

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8
Q

what happens due to interaction of PPIs with cytochrome p450 isoenzymes?

A

decrease the anti platelet activity of clopidogrel

increase the effect of phenytoin and warfarin

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9
Q

administration of PPIs

A

once daily in the morning PO before food

IV to treat recurrent ulcer bleeding in high risk patients

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10
Q

example of histamine type 2 receptor antagonists

A

ranitidine

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11
Q

mechanism of action of H2 receptor antagonists

A

competitive antagonism of the H2 receptor located on the basolateral membrane of acid secreting parietal cells of the gastric glands

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12
Q

PPIs are more effective than H2 receptor antagonists

A

TRUE

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13
Q

indications for H2 receptor antagonists

A
  1. peptic ulcer disease (prevention and treatment)

2. dyspepsia and GORD (symptomatic relief)

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14
Q

adverse effects of H2 receptor antagonists

A
  • diarrhoea
  • less commonly constipation
  • headache
  • abdominal pain
  • dizziness
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15
Q

what may H2 receptor antagonists and PPIs disguise the symptoms of?

A

gastric cancer

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16
Q

administration of H2 receptor antagonists

A

PO twice daily

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17
Q

name anti motility drugs

A

loperamide

codeine phosphate

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18
Q

mechanism of action of loperamide

A

synthetic opioid with agonist activity at u opioid receptors expressed by enteric neurones of the GIT

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19
Q

effect of loperamide and codeine

A

increases the tone and rhythmic contractions of the intestine
constricts smooth muscle sphincters
inhibits peristalsis
= constipating

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20
Q

when is codeine preferred over loperamide?

A

when additional analgesia is required

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21
Q

indications for anti motility drugs

A
  1. acute diarrhoea (symptomatic relief)
  2. diarrhoea associated with IBS (symptomatic relief)
  3. analgesia for acuter moderate pain
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22
Q

adverse effects of anti motility drugs

A

constipation
abdominal cramping
flatulence

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23
Q

contraindications for anti motility drugs

A

acute UC (risk of megacolon and perforation)
acute bloody diarrhoea (dysentery
C diff colitis

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24
Q

when can anti motility drugs be prescribed in the hospital setting?

A

once the probable cause has been identified and c diff is excluded

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25
who should anti motility drugs be prescribed to?
children under 4
26
administration of anti motility drugs
PO as capsule or tablet
27
name a bulk forming laxative
ispagula husk
28
what are bulk laxatives?
hydrophilic agents which are indigestible
29
mechanism of action of bulk laxatives
by osmosis, water is attracted to the stool, increasing bulk and stimulating peristalsis
30
what is important for the action of bulk laxatives?
adequate fluid ingestion
31
indications for bulk laxatives
1. constipation and faecal impaction | 2. mild chronic diarrhoea associated with diverticular disease or IBS
32
adverse effect of bulk laxatives
rarely may cause faecal impaction and GI obstruction
33
when should bulk laxatives be avoided?
patients at risk of or suffering from intestinal obstruction ileus
34
administration of bulk laxatives
PO (as powders, granules, tablets) | around meal times with plenty of water
35
name osmotic laxatives
lactulose macrogols citrate and phosphate enemas
36
what are osmotic laxatives?
osmotically active agents which are neither digested nor absorbed
37
mechanism of action of osmotic laxatives
by osmosis, water is attracted to the stool, increasing bulk and stimulating peristalsis
38
why is lactulose helpful in patients with renal failure?
reduces ammonia absorption by decreasing transit time, acidifying the stool and inhibiting the proliferation of ammonia producing bacteria
39
indications for osmotic laxatives
1. constipation and faecal impaction 2. bowel preparation before endoscopy or surgery 3. hepatic encephalopathy
40
adverse effects of phosphate enemas
local irritation and electrolyte disturbance
41
contraindications for osmotic laxatives
intestinal obstruction (risk of perforation)
42
when should phosphate enemas be used with caution?
patients with heart failure and where electrolyte disturbances are present
43
administration of osmotic laxatives
PO as powders dissolved in water or liquids with or without food as enema, once only or as required but no more than once daily
44
name stimulant laxatives
Senna bisocodyl glycerol suppository docusate sodium
45
mechanism of action of stimulant laxatives
increase water and electrolyte secretion from the colonic mucosa colonic content is increased by stimulating peristalsis
46
what additional action does decussate sodium have?
faecal softening
47
indications for stimulant laxatives
1. constipation | 2. faecal impaction (as suppository)
48
adverse effects of stimulant laxatives
prolonged use may cause an irreversible atonic colon and reversible melanosis coli
49
contraindications for stimulant laxatives
intestinal obstruction (risk of perforation)
50
when should rectal preparations of stimulant laxatives be avoided?
in patients with anal fissures or haemorrhoids
51
administration of stimulant laxatives
for constipation PO | for faecal impaction, as suppository, once only or as required but no more than once daily
52
name dopamine D2 receptor antagonists
domperidone | metoclopramide
53
mechanism of action of domperidone
antagonist of dopamine D2 receptors in the CTZ but does not cross the BBB
54
additional action of metoclopramide
additional activity as an antagonist at 5-HT3 receptors and as an agonist at 5-HT4 receptors
55
indications for D2 receptor antagonists
1. treatment of nausea and vomiting particularly when reduced gut motility is evident eg drug or chemotherapy induced nausea and vomiting 2. treatment of GORD (as an add-on to patients who do not respond to H2 antagonists or PPIs) 3. vomiting associated with emergency hormonal contraception
56
adverse effects of D2 receptor antagonists
- diarrhoea | - metoclopramide may cause extra pyramidal symptoms
57
contraindications to D2 receptor antagonists
GI obstruction and perforation
58
when is metoclopramide best avoided?
in children and young adults in which extra pyramidal side effects are most common
59
administration of D2 receptor antagonists
PO up to three times a day | metoclopramide is available IV, IM or injection
60
name histamine H1 receptor antagonists
cyclizine | cinnarazine
61
mechanism of action of H1 receptor antagonists
competitive antagonism of H1 receptors in the VC | additional block of muscarinic ACh receptors in the vestibular apparatus probably contributes to their effectiveness
62
indications for H1 receptor antagonists
1. motion sickness and vertigo | 2. post operative nausea and vomiting
63
adverse effects of H1 receptor antagonists
- drowsiness and sedation - reduce saliva leading to dry mouth - IV may cause a transient tachycardia
64
when should H1 receptor antagonists be avoided?
in patients at high risk of hepatic encephalopathy or those with prostatic hyperplasia
65
administration of H1 receptor antagonists
PO regularly, or as required | cyclizine may be given IM or IV or injection
66
name a phenothiazine
procloperazine
67
mechanism of action of phenothiazine
involves competitive antagonism of D2, H and M1 receptors in the vomiting centre, vestibular system and peripherally in the gut
68
indications for phenothiazines
1. vertigo 2. sometimes chemo induced nausea and vomiting 3. schizophrenia
69
adverse effects of phenothiazines
- drowsiness - postural hypertension - long term treatment = tardive dyskinesia or Parkinsonism - QT interval prolongation
70
when to avoid phenothiazines?
in severe liver disease (potential for hepatotoxicity) | in prostatic hyperplasia
71
when to reduce the dose of phenothiazines?
in elderly patients as they may be liable to confusion
72
administration of phenothiazines
orally or deep IM for acute episode with further oral doses as necessary
73
name the 5-HT3 receptor antagonist
ondansetron
74
mechanism of action of 5-HT3 receptor antagonists
competitive antagonism of inotropic 5-HT3 receptors which are located in the CTZ, NTS and also peripherally on the terminals of vagal afferent fibres innervating the GI tract
75
indications for 5HT3 receptor antagonists
1. chemo and radiotherapy nausea and vomiting 2. post operative nausea and vomiting 3. IBS 4. hyperemesis gravidarum
76
adverse effects of 5HT2 receptor antagonists
- constipation - diarrhoea - headaches
77
contraindications for 5HT3 receptor antagonists
``` severe or prolonged constipation intestinal obstruction stricture toxic megacolon ischaemic colitis Crohn's disease UC diverticulitis ```
78
when should ondansetron be avoided?
patients with a prolonged QT interval or who are taking drugs which prolong the QT interval
79
administration of andansetron
PO PR IM IV

GI (9 decks)

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