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Clinical Pharmacology And Therapeutics > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

What are the primary goals in treatment of dyspepsia

A

Symptom relief
- avoidance of causative drugs and food eg chocolate
- GORD: propping up bed, removing belts
- suppression of acid release and mucosal protection

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2
Q

Describe the curative treatment of dyspepsia

A

Suppression of acid release to allow natural healing and eradication of H pylori infection
Reduction of risk of gastric carcinoma

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3
Q

Describe the mode of action of antacids

A

Anti acid used to raise pH and treat dyspepsia

Provide rapid relief but not cure

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4
Q

What are alginates

A

Combined with antacids
Derived from alginic acid and forms a viscous foam when combined with saliva
Floats on the gastric contents forming a raft which protects the oesophagus during reflux

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5
Q

What do histamine H2 antagonists do

A

Reduce gastric acid secretion
Provide symptomatic relief
Best given at night
Promote ulcer healing
Reduce the need for surgery in ulceration
H1 receptor antagonists are antihistamines

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6
Q

What is the mode of action of PPIs

A

Act via irreversible inhibition of the proton pump

They are activated by acidic pH

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7
Q

What are some adverse effects of PPIs

A

Inhibit H+ secretion by >90% which can lead to achlorhydria and increase risk of campylobacter infection

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8
Q

Why should alcohol be avoided when taking metronidazole

A

Metronidazole inhibits the breakdown of alcohol at the aldehyde stage

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9
Q

What are ways of minimising GI damage

A

Use paracetamol for analgesia
Identify pts at risk eg over 65, history of ulcers
Prophylaxis with PPI
Use PPI over H2 antagonists as they are less effective
Give in combination with misoprostol - acts on prostanoid receptors to inhibit gastric H+ secretion

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10
Q

Which drugs cause nausea

A

Anti cancer agents
Digoxin
SSRIs
Opioids
Levodopa
Erythromycin

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11
Q

What is the pathway by which motion causes sickness

A

Labyrinth acts on the vestibular nuclei (H1 and M receptors)
These act on the chemoreceptor trigger zone D2 and 5HT3 receptors
Which acts on the vomiting centre

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12
Q

How do drugs and toxins cause vomiting

A

They act directly on the chemoreceptor trigger zone D2 and 5HT3 receptors which acts on the vomiting centre

They can also act on the visceral afferents 5HT3 receptors which acts on the nucleus of the solitary tract which acts directly on the vomiting centre

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13
Q

What is the main anti emetics used

A

H1 receptor antagonists eg promethazine, cyclizine

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14
Q

Mode of action of H1 receptor antagonists

A
  • act on the vestibular nuclei
  • effective in motion sickness
  • have anti-muscarinic actions
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15
Q

How do anti muscarinic agents eg hyoscine work

A

Effective in motion sickness and irritation of the stomach
Have anti muscarinic side effects

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16
Q

How do dopamine antagonists work as anti emetics

A

Acts in CTZ but has unwanted CNS effects
- effective against anti cancer drug induced Emesis

17
Q

How do 5-hydroxytryptamine antagonists work

A

Block 5 HT at 5HT3 receptors in the gut and CNS
Effective against anti cancer drugs and post operative N&V

18
Q

Give examples of drugs that can cause diarrhoea

A

Antibiotics: alter lower GI flora, clindamycin associated with pseudomembraneous colitis

Orlistat: pancreatic lipase inhibitor that causes fatty diarrhoea

Misoprostol: via cAMP

PPIs: infection

19
Q

How is diarrhoea treated

A

Oral rehydration therapy eg dioralyte
Is a solution of electrolytes to replace the electrolytes lost
Must be isotonic

20
Q

How can diarrhoea be relieved symptomatically

A

Antimotility agents
Codeine and loperamide. If infection is present they can prolong the infection and prevent clearance

21
Q

Why is loperamide used over codeine

A

Doesnt penetrate BBB and has efficient enterohepatic cycling so retained largely in the GI tract

Codeine has some potential neuro side effects

22
Q

What is irritable bowel syndrome

A

A common long standing disorder
Present for at least 3 days per month in the last 3 months:
- abdo pain
- bloating relieved by defecation
- change in bowel habit

23
Q

What is inflammatory bowel disease

A

Includes crohn’s and UC
- inflammatory conditions with high degree of morbidity and run relapsing and remitting courses

Causes are unclear

24
Q

Describe the clinical symptoms of acute gastroenteritis

A

Diarrhoea >3 loose stools per day
N&V
Abdo pain
Fever

25
Q

What is dysentery

A

Bloody diarrhoea

26
Q

What % of antibiotic associated diarrhoea is C diff positive

A

20-30%

27
Q

What % of antibiotic associated colitis is C diff positive

A

50-75%

28
Q

What % of pseudomembranous colitis is C diff positive

A

> 90%

29
Q

Why are antibiotics not given for travellers bacteria

A

<80% due to bacteria and are due to a virus

People usually get better by themselves

Clinical Pharmacology And Therapeutics (7 decks)

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