Pharmacology of upper and lower GI tract drug treatments Flashcards

1
Q

What cell secretes Gastric acid and is responsible for ulceration and inflammation?

A

Parietal cell

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2
Q

What are the four controls of acid secretion?

A

1) ACH (Vagal nerve control)
2) H2 receptor (Histamine)
3) Gastrin (triggered by diet)
4) PGE2 (prostaglandin)
- only prostaglandin decreases acid release rest increase
- Each affect H+/K+ ATPase proton pump

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3
Q

What is a peptic ulcer?

A

Defect in the gastric or duodenal mucosa caused by an increase in acid secretion

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4
Q

What are the three things that need to be done when treating peptic ulcer?

A

1) pain relief
2) Heal Ulcer
3) Prevent relapse or complications
4) Ensure not gastric carcinoma

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5
Q

What are the five treatments types for peptic ulcers?

A

1) Remove irritants (drugs or dietary)
2) Antacids
3) Proton Pump inhibitors
4) H2 receptor antagonists
5) Antibiotics (if H Pylori present)

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6
Q

How can NSAIDs cause ulceration?

A
  • NSAIDs act on COX1 and COX2
  • COX1 responsible for prostaglandin synthesis
  • when inhibited by NSAIDs Prostaglandin can’t decrease acid secretion
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7
Q

What are the other major causes of Ulceration?

A

1) Aspirin
2) Corticosteroids
3) Bisphosphonates (mucosal toxic)
4) Nicotine
5) Alcohol
6) Caffeine
7) Severe stress (increases acid sec)
8) Hypersecretory states (uncommon)

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8
Q

What bacteria can cause Ulcers?

A

Helicobacter Pylori

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9
Q

What are the most common antacids?

A

Magnesium and aluminium salts often combination

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10
Q

What are the disadvantages of antacid use?

A

1) only symptomatic relief won’t actually decrease acid over production so only effective briefly
2) Antacids which are too well absorbed can metabolic alkalosis in blood

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11
Q

What are the main Proton Pump Inhibitors?

A
  • Omeprazole (irreversible)
  • Lansoprazole
  • Pantoprazole
  • Esomeprazole
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12
Q

What is the MOA of Proton pump Inhibitors?

A

Inhibit H+/K+ Proton pump in parietal cells to prevent acid secretion

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13
Q

What are the adverse reactions of omeprazole?

A

Common: GI disturbance (vomiting, diarrhoea or constipation) and headaches
Important: Inc risk of C Diff and pneumonia, hyponatraemia, hypomagnesaemia, CKD, liver problems and blood disorders e.g. dec platelets or WBCs

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14
Q

What drugs does omeprazole interact with

A

1) Warfarin = increases anticoagulant effects as CYP450 enzyme inhibited so warfarin not metabolised
2) Clopidogrel = less activated as hepatic pro-drug, reduce anti platelet effects

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15
Q

Why might PPIs be contraindicated?

A

1) reduction in efficacy of clopidogrel but lansoprazole can be used instead (less CYP450 inhibition) usually necessary in post NSTEMI patients
2) Can get rebound effect where cells secrete more cells in response to drugs but shorter treatment times decrease likelihood

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16
Q

What are the common H2 receptor antagonists?

A

Cimetidine

Ranitidine

17
Q

What do H2 Receptor antagonists target?

A

Target Histamine receptor so reduce histamines signalling and less acid secreted

18
Q

What are the adverse side effects of Cimetidine?

A

Gynaecomastia in men
confusion in older patients
Diarrhoea
Potent CYP450 inhibitor so doesn’t interact well with other drugs, any CYP450 metabolised drugs not processed well so many side effects

19
Q

Why may Ranitidine be preferred over Cimetidine?

A

1) less potent inhibitor so less interactions
2) No gynaecomastia or confusion
3) But do contain microscopic traces of carcinogens so aren’t used much

20
Q

Pathology of H Pylori?

A

Found in mucous layer and secrete urease which converts urea to ammonia and CO2, these products cause inflammation and erode mucosal layer

21
Q

What is the test for H pylori?

A
  • Use Carbon-13 urea breath test
  • Give sample of Urea labelled with C13
  • take breath sample 30 mins later, if C13 present in CO2 the positive test
  • serology test will show pos test even if recovered
  • GI endoscopy also possible Pink if pos
22
Q

Treatment for H Pylori?

A
  • Eradication therapy which involves two antibiotics and a PPI/H2 receptor antagonist
  • for 7 days but can need for a little longer
23
Q

What antibiotics are usually used in the eradication therapy?

A

Clarithromycin

Amoxicillin or metronidazole

24
Q

When should an urgent upper GI endoscopy be done?

A

Red flag symptoms: GI bleed, Weight loss, dysphagia and vomiting
GI bleed may only show as anaemia if chronic
be more wary of those over 55

25
Q

What are the non-pharmacological treatments for constipation?

A
  • increase fluid
  • increase fibre intake
  • increase mobility
  • stop constipating drugs
26
Q

What are the constipating drugs?

A

Opioids
anti-muscarinics e.g. anti-depressants
diuretics

27
Q

What are non-drug causes of constipation?

A
  • Pain when passing bowel motions e.g. haemorrhoids
  • Hypercalcaemia
  • Hyperthyroidism
  • Diabetes
  • Tumours
28
Q

What are the four types of laxative

A
  • Bulk (Fybrogel) make stool soft and easy to pass
  • Stimulant (Senna) stimulate enteric nervous system to promote peristalsis
  • Osmotic (Macrogels) pull water into gut lumen
  • Faecal softener (docusate) less commonly used
29
Q

How is constipation treated?

A
  • Try non-pharm first
  • Pre-empt if giving opioids give osmotic and stimulant (not bulk)
  • First line usually Bulking and osmotic