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Medicine > GI Pharmacology > Flashcards

GI Pharmacology Flashcards

1
Q

What are some ways for managing peptic ulcer with drugs

A

Reducing gastric acid secretion
Neutralizing secreted gastric acid
Increase mucosal resistance to acid-pepsin attacks
Eradicating H. pylori

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2
Q

What classes of drugs could help in reducing gastric acid secretion

A

H2-receptor antagonists
Proton pump inhibitors and
Muscarinic receptor antagonists

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3
Q

What class of drug could be used to neutralize secreted gastric acid

A

Antacids

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4
Q

Which class of drugs could be used to Increase mucosal resistance to acid-pepsin attacks

A

Misoprostol or chelates

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5
Q

What is the MOA of histamine H2 receptor antagonists

A

Competitive blockade of histamine on the H2 receptor

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6
Q

What are some examples of histamine H2 receptor antagonist drugs

A

Cimetidine and ranitidine

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7
Q

What are some indications for histamine H2 receptor antagonists

A

Peptic ulcer and GORD

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8
Q

What are some contraindications for cimetidine

A

Cimetidine not given to patients stabilized on warfarin, phenytoin, and theophylline

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9
Q

What are some adverse effects of histamine H2 receptor antagonists

A

Dizziness
Fatigue
Rashes
Low sperm count due to antiandrogenic effects

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10
Q

What are some examples of PPIs

A

Omeprazole, Esomeprazole

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11
Q

What is the MOA of PPIs

A

Irreversible inhibition of H+/K+ ATPase responsible for proton secretion from parietal cells. They are pro-drugs, converted at acid pH to sulphonamide, which combines covalently with sulphydryl groups on the H+/K+ ATPase

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12
Q

What are some indications of PPI

A

Short-term treatment of peptic ulcers, eradication of H. pylori, oesophagitis, Zollinger-Ellison syndrome

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13
Q

What are some adverse effects of PPIs

A

GI upsets, nausea, headaches, gastric atrophy with long term treatment

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14
Q

What are some examples of muscarinic receptor antagonists

A

Atropine
Pirenzepine
Dicyclomine (dicycloverine)

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15
Q

What is the MOA of muscarinic receptor antagonists

A

Inhibition of parasympathetic activity, causing relaxation of GI smooth muscle as well. They may be of value in peptic ulcer since the condition may be accompanied by increased muscle spasm

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16
Q

What are the indications of muscarinic receptor antagonists

A

As adjuncts in the management of peptic ulcer

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17
Q

What is an example of a mucosal strengthener drug

A

Misoprostol

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18
Q

What is the MOA of mucosal strengtheners

A

Synthetic analogue of PG E, imitating the action of endogenous PGE2 and PGI2, thereby maintaining the
integrity of the gastroduodenal barrier. It therefore promotes healing

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19
Q

What are some indications for given mucosal strengtheners

A

Ulcer healing and prophylaxis with NSAID use

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20
Q

What are some contraindications of mucosal strengtheners

A

Hypotension, pregnant and
breast-feeding women

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21
Q

What are some adverse effects of mucosal strengtheners

A

Diarrhoea, nausea and abdominal pain

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22
Q

What are some examples of chelates

A

Bismuth chelate and sucralfate

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23
Q

How do chelates protect the mucosa

A

Inhibiting the action of pepsin
Promoting the synthesis of protective prostaglandins
Stimulating the secretion of bicarbonate

They are given orally and well tolerated

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24
Q

Give some examples of neutralizing secreted acid with antacids

A

Aluminium hydroxide, magnesium hydroxide and sodium bicarbonate

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25
Q

What is the MOA of antacids

A

Antacids consist of alkaline Al3+, Mg2+ and Na+ salts that are used to raise the luminal pH of the stomach
They neutralize acid and as a result, may reduce the damaging effects of pepsin which is pH dependent.
Additionally, Al3+ and Mg2+ salts bind and inactivate pepsin

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26
Q

What are some indications for antacids

A

Symptomatic relief of ulcers and GORD

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27
Q

What are some contraindications of antacids

A

Aluminium and magnesium hydroxides should not be given to patients with hypophosphataemia
Sodium bicarbonate should be avoided in patients on a salt-restricted diet (e.g. heart failure and in hepatic and renal impairment)

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28
Q

What are some side effects of neutralizing secreted acid with antacids

A

Constipation and diarrhea
Sodium Bicarbonate may lead to alkalosis
Complexation with tetracyclines

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29
Q

Talk about alginates

A

Alginate containing antacids (eg. Gaviscon) are administered orally
It forms an impenetrable raft that floats on the surface of the gastric contents. The layer prevents gastric acid from refluxing into the oesophagus, useful in GORD
It is well tolerated but no effect upon acid secretion or healing

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30
Q

Give some facts about H. pylori in relation to peptic ulcer

A

H. pylori plays a significant role in the pathogenesis of ulcer
It does not cause ulcer in all infected patients (50-80%)
90% of ulcer patients have H. pylori infection
Rate of recurrence of duodenal ulcers relatively low with H. pylori eradication regimes compared with non-involvement of H. pylori eradication regimes

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31
Q

What are some current eradication regimes for H. pylori

A

Classic therapy: omeprazole, clarithromycin, amoxycillin or metronidazole , tetracycline for 1 or 2 weeks. 90% elimination, but compliance, resistance and adverse effects!
Dual therapy: Omeprazole + single antibiotic, amoxycillin or Clarithromycin-less effective

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32
Q

What is nausea

A

It is an unpleasant feeling in the upper abdomen and throat which usually precedes vomiting.
It may be experienced without vomiting

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33
Q

What is vomiting

A

Vomiting is the forceful expulsion of GIT contents through the mouth

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34
Q

Which part of the brain stem is responsible for nausea and vomiting

A

The vomiting centre and the chemoreceptor trigger zone (CTZ) in the brainstem are responsible for the central regulation of nausea and vomiting

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35
Q

Describe what the CTZ contains

A

The CTZ contains dopamine and serotonin receptors. It receives input from H1 receptors in the vestibular nuclei. The vomiting centre contains muscarinic receptors

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36
Q

What are some causes of nausea and vomiting

A

GI irritation
Motion sickness
Vestibular disease
Hormonal disturbances
Drugs and radiation
Exogenous toxins
Pain
Psychogenic factors
Intracranial pathology

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37
Q

A liquid causes gastric irritation resulting in emesis to relieve nausea
What is the name of this liquid

A

Ipechacuanha

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38
Q

What is one positive use of vomiting

A

Emesis (vomiting) may be induced to rid the GIT of ingested exogenous toxins

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39
Q

What are some classes of antiemetic drugs

A

H1 receptor antagonists
Phenothiazines
Dopamine antagonists
5-HT3 receptor antagonists

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40
Q

What are some examples of H1 receptor antagonists

A

Cyclizine and cinnarizine (stugeron)

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41
Q

These are antiemetic antihistamines. They have little effect on nausea and vomiting induced by substances acting directly on the CTZ. They are however effective in motion sickness and vestibular disorders
What class of drug is this

A

H1 receptor antagonist

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42
Q

What are the routes of administration of cyclizine and cinnarizine

A

Cyclizine (Oral, IM. IV)
Cinnarizine (Oral)

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43
Q

What are the indications of H1 receptor antagonists

A

Motion sickness
Vestibular disorders

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44
Q

What are some adverse effects of H1 receptor antagonists

A

Drowsiness, dry mouth, blurred vision

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45
Q

What are some cautions in using a H1 receptor antagonists

A

Use with caution in urinary retention, glaucoma

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46
Q

What is the most widely used antiemetic in the class of phenothiazines

A

Prochlorperazine (Stemetil) is the most widely used antiemetic in this class

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47
Q

What is the MOA of phenothiazines

A

Numerous effects; It blocks dopaminergic, histaminic and muscarinic receptors

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48
Q

What are the routes of administration for phenothiazines

A

Oral, rectal and intramuscular

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49
Q

What are some indications for phenothiazines

A

Nausea, vomiting, vertigo, psychosis

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50
Q

What are some contraindications for phenothiazines

A

It may exacerbate Parkinsonian symptoms

51
Q

What are some adverse effects of phenothiazines

A

Sedation
Postural hypotension
Extrapyramidal symptoms

52
Q

What are some examples of dopamine antagonist drugs

A

Domperidone (Motilium) and metoclopramide (Maxolon)

53
Q

What is the MOA for dopamine antagonist drugs

A

They block dopamine receptors and act on the CTZ. Their antiemetic effect is enhanced by promoting gastric emptying and small intestine peristalsis.

54
Q

What is the route of administration for metoclopramide or domeperidone

A

Metoclopramide (Oral, IM, IV) Domperidone (Oral, Rectal)

55
Q

What are some indications for dopamine antagonists

A

Nausea and vomiting

56
Q

What are some contraindications to metoclopramide, a dopamine antagonist

A

Metoclopramide not given to patients under 20 due to increased risk of extrapyramidal side effects

57
Q

Give an example of a 5-HT3 receptor antagonists

A

Ondansetron

58
Q

What is the MOA for 5-HT3 receptor antagonists

A

Antagonism of 5-HT3 (serotonin) receptor in the CTZ is believed to be responsible for the antiemetic effects

59
Q

What are the routes of administration for 5-HT3 receptor antagonists

A

Oral, rectal, intramuscular, iv

60
Q

What are some indications for 5-HT3 receptor antagonists

A

Nausea & vomiting especially associated with cytotoxic therapy

61
Q

What are some adverse effects of 5-HT3 receptor antagonists

A

Constipation & headache

62
Q

What are some classes of drugs which affect intestinal motility

A

Motility stimulants
Antispasmodics
Laxatives
Antidiarrhoeals

63
Q

What are motility stimulants

A

Agents that increase GI motility without a laxative effect are used clinically for motility disorders. Eg. GORD, Gastric stasis (slow stomach emptying), Diagnostics e.g. Duodenal intubation

64
Q

Which two drugs increase intestinal
motility by unknown mechanisms

A

Domperidone and metoclopramide

65
Q

What are the two classes of antispasmodics

A

Antimuscarinics
Drugs acting directly on smooth muscle

66
Q

Antispasmodics have smooth muscle relaxant properties, therefore useful as adjuncts for which diseases

A

Non-ulcer dyspepsia
Irritable bowel syndrome
Diverticular disease

67
Q

Give two examples of antimuscarinics

A

Propantheline, dicycloverine (dicyclomine)

68
Q

What is the MOA for antimuscarinics

A

Inhibition of parasympathetic activity
Causing relaxation of GI smooth muscle

69
Q

What is the route of administration for antimuscarinics

A

Oral

70
Q

What are some indications for antimuscarinics

A

Non-ulcer dyspepsia
Irritable bowel syndrome
Diverticular disease

71
Q

What are some contraindications for antimuscarinics

A

Antimuscarinic drugs relax the LOS therefore should be avoided in GORD, also myasthenia gravis

72
Q

What are some adverse effects of antimuscarinics

A

Dry mouth
Blurred vision
Dry skin
Tachycardia
Urinary retention

73
Q

What are some examples of drugs acting directly on smooth muscle

A

Mebeverine, alverine, peppermint oil

74
Q

What is the MOA for drugs acting directly on smooth muscle

A

Direct relaxants of smooth muscle

75
Q

What is the route of administration for drugs acting directly on smooth muscle

A

Oral

76
Q

What are some indications for drugs directly acting on the smooth muscle

A

Irritable bowel syndrome
Diverticular disease

77
Q

What are laxatives

A

They are drugs used to hasten transit time in the gut and encourage defecation. They are useful to prevent undue straining at stool as this may produce hernia

78
Q

Laxatives/purgatives may be given to

A

To remove poisons from the alimentary canal
Prepare patients for radiological examination of the colon
Remove parasites from the body after anthelminitic therapy
Empty the bowel before surgery
Counteract the constipating effect of drugs

79
Q

What are some other terms used in place of laxative

A

Aperient
Lenitive
Laxative
Evacuative
Purgative
Cathartic

Arranged in order of increasing severity.
Effect however depends on:
Dose
The individual
The agent

80
Q

Mention the types of laxatives

A

Bulk-forming laxatives
Osmotic laxatives
Stimulant laxatives
Faecal softners

81
Q

What are some examples of bulk-forming laxatives

A

Bran
Methyl-cellulose
Ispaghula husk

82
Q

What are some examples of osmotic laxatives

A

Lactulose and saline purgatives

83
Q

What are some examples of stimulant laxatives

A

Senna, danthron, bisacodyl, sodium picosulphate, castor oil

84
Q

What are some examples of faecal softeners

A

Liqiud paraffin, docusate sodium

85
Q

What is the MOA for bulk forming laxatives

A

They increase the volume of non-absorbable solid residue in the gut, causing distending of the colon and stimulating peristalsis

86
Q

What is the ROA for bulk forming laxatives

A

Oral

87
Q

What are some indications of bulk forming laxatives

A

Constipation

88
Q

What are some adverse effects of bulk forming laxatives

A

Flatulence, abdominal distension, GI obstruction

Note: Adequate fluid intake is encouraged, onset may be several days

89
Q

What is the MOA for osmotic laxatives

A

Poorly absorbed substances that increase the water content of the bowel by osmosis
Lactulose, a semi-synthetic disaccharide not absorbed from the GIT. Magnesium and sodium salts are poorly absorbed and can be osmotically active

90
Q

What is the ROA of osmotic laxatives

A

Oral

91
Q

What is the indication for osmotic laxatives

A

Constipation

92
Q

What are some contraindications to bulk forming laxatives

A

Intestinal obstruction, colonic atony, dysphagia

93
Q

What are some contraindications to osmotic laxatives

A

Intestinal obstruction

94
Q

What is the MOA for stimulant laxatives

A

Increase GI peristalsis and water and electrolyte secretion by the mucosa possibly by stimulating enteric nerves

95
Q

What is the ROA for stimulant laxatives

A

Oral and rectal

96
Q

What are the indications of stimulant laxatives

A

Constipation and bowel evacuation prior to medical/surgical procedures

97
Q

What is the contraindication for stimulant laxatives

A

Intestinal obstruction

98
Q

What are some adverse effects of stimulant laxatives

A

Intestinal cramps, possible damage to nerve plexi leading to deterioration of intestinal function and atonic colon. Danthron, potentially carcinogenic.

Note: Give stimulant laxatives for short periods only

99
Q

What is the MOA for lubricants

A

Promote defaecation by softening (Docusate sodium) and/or by lubricating (liqiud paraffin) faeces to aid their passage through the GI tract

100
Q

What are the ROAs for lubricants

A

Oral, docusate sodium can be given rectally.

101
Q

What are some indications for lubricants

A

Constipation, haemorrhoids

102
Q

What are some contraindications to lubricants

A

Not in children less than 3 years

103
Q

What are some adverse effects of lubricants (fecal softeners)

A

Prolonged use of liquid paraffin impairs the absorption of fat-soluble vitamin A and D

Note: Prolonged use not recommended

104
Q

What are the four approaches to the treatment of severe acute diarrhea

A

Maintenance of fluid and electrolyte balance through Oral Rehydration Therapy (ORT)
Use of anti-microbial drugs
Use of opiate-like anti-motility drugs
Use of stool modifiers and adsorbents

105
Q

Should be the first priority in the treatment of acute diarrhoea
What therapy is this

A

Oral rehydration therapy

106
Q

What does a standard ORT contain

A

NaCl
KCl
Sodium citrate
Glucose in appropriate concentrations

IV rehydration therapy recommended if dehydration is severe

107
Q

What are some functions of zinc supplements

A

Protein synthesis,
Cell growth and differentiation,
Immune function,
Intestinal transport of water and electrolytes

Zinc deficiency is associated with an increased risk of gastrointestinal infections and impaired immune function

108
Q

Which antibiotic is used to treat severe cholera or salmonella typhimurium infection

A

Tetracycline

109
Q

Which antibiotic treatment is used in Shigella-caused diarrhea

A

Ampicillin

110
Q

Which antibiotic treatment is used in Campylobacter jejuni - caused diarrhea

A

Erythromycin or Cipro

111
Q

Which antibiotic is given in an amoebic diarrhoea, giardiasis

A

Metronidazole

112
Q

What are some examples of opiate-like antimotility drugs

A

Loperamide & codeine

113
Q

What is the MOA for opiate-like antimotility drugs

A

These act on opioid receptors in the GIT which increases the tone and rhythmic contraction of the intestine, but lessens propulsive activity
Decrease in propulsive activity leads to an increase in transit time and hence absorption of electrolyte
Overall effect is constipation.
Loperamide and codeine also have an antisecretory action

114
Q

Which opiate-like antimotility drugs also have an anti-secretory action

A

Loperamide and codeine

115
Q

What is the ROA for opiate-like antimotility drugs

A

Oral

116
Q

What are some indications for opiate-like anti-motility drugs

A

They have a limited role as an adjunct to fluid and electrolyte replacement in acute diarrhoea. Also as adjunctive therapy in some chronic diarrhoeal conditions

117
Q

What are some contraindications to opiate-like anti-motility drugs

A

Acute ulcerative colitis or antibiotic associated colitis. Not recommended for children

118
Q

What are some adverse effects of opiate-like anti-motility drugs

A

Nausea, vomiting, abdominal cramps, constipation, drowsiness

119
Q

What is the MOA for stool modifiers/adsorbents

A

Adsorption of toxins or coating and protecting the intestinal mucosa.
They also add solid matter to the colonic contents and improve the consistency of the faeces

120
Q

What are some examples of stool modifiers/adsorbents

A

Kaolin, chalk, charcoal, ethylcellulose, pectin

121
Q

What is the ROA for stool modifiers

A

Oral

122
Q

What are some contraindications for stool modifiers

A

Not recommended for acute diarrhea

123
Q

What are some adverse effects of stool modifiers

A

Inhibit the absorption of other drugs

Medicine (38 decks)

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