GI Pharmacology

Question 1

Risk factors of gastric and duodenal ulcers

Answer 1

• Helicobacter pylori
• NSAIDs
• early gastric emptying
• smoking + alcohol delay healing

Question 2

Common causes of gastric + duodenal ulcers

Answer 2

Helicobacter pylori (most common)
NSAIDs

Question 3

Example of alginates + antacids

Answer 3

Gaviscon

Question 4

What class of drug is gaviscon?

Answer 4

Alginate + antacid

Question 5

What are the uses of gaviscon?

Answer 5

GORD

Question 6

What is the mechanism of action of gaviscon?

Answer 6

• antacid: buffers stomach acid
• alginic acid: increase stomach content viscosity + reduce reflux

Question 7

What is gaviscon composed of?

Answer 7

• alginic acid: sodium alginate
• antacid: aluminium hydroxide/magnesium carbonate

Question 8

What are adverse drug reactions of gaviscon?

Answer 8

Magnesium salts can cause diarrhoea
Aluminium salts can cause constipation

Question 9

Why is the antacid part of gaviscon often composed of both aluminium hydroxide AND magnesium carbonate?

Answer 9

• magnesium salts can cause diarrhoea
• aluminium salts can cause constipation
• attempt to balance out the adverse drug reactions
  .
• magnesium hydroxide gastric pH higher + faster than aluminium hydroxide (AlHO has longer duration)

Question 10

What are contradictions of gaviscon?

Answer 10

• renal failure in Na+ + K+ containing preparations
• diabetes mellitus in high sucrose conc preparations

Question 11

What are important drug drug interactions of gaviscon?

Answer 11

• Can reduce absorption of drugs so doses should be separated
• Increased urine alkalinity can increases aspirin excretion

Question 12

Examples of proton pump inhibitors

Answer 12

Omeprazole
Lansoprazole

Question 13

What are the uses of PPIs?

Answer 13

Helicobacter pylori eradication
Peptic ulcers + relapse prevention
Co prescribed within NSAIDs

Question 14

What is the mechanism of action of PPI?s

Answer 14

Irreversibly inhibition H+/K+ ATPase in parietal cells > reduction in acid secretion

Question 15

What are adverse drug reactions of PPIs?

Answer 15

• abdominal pain
• diarrhoea
• constipation
• headache
• dizziness
• drowsiness
• can mask symptoms of gastro-oesophageal cancer

Question 16

What are important drug drug interactions of PPIs?

Answer 16

• Omeprazole is a CYP inhibitors > reduced clopidogrel action
• increased effects of warfarin + phenytoin

Question 17

What is the suffix of PPIs?

Answer 17

-prazole

Question 18

Example of H2 receptor antagonists

Answer 18

Ranitidine

Question 19

What are uses of H2 receptor antagonists?

Answer 19

Peptic ulcers
GORD

Question 20

What is the mechanism of action of H2 receptor antagonists?

Answer 20

• Inhibition of H2 receptors
• Reduces release of histamines
• Reduces acid secretion from parietal cells

Question 21

What are adverse drug reactions of H2 receptor antagonists?

Answer 21

Generally well tolerated
Diarrhoea
Headache
Can mask symptoms of gastro-oesophageal cancer

Question 22

What are important drug drug actions of H2 receptor antagonists?

Answer 22

Few common

Question 23

A patient is taking clopidogrel + the doctor wants to prescribe a PPI for their duodenal ulcer. Which PPI should they be given + why?

Answer 23

Lansoprazole
Omeprazole is a CYP inhibitor > reduces clopidogrel action

Question 24

How should a PPI be prescribed?

Answer 24

Shorted effective duration at lowest effective dose

Question 25

Treatment of Helicobacter pylori infection - triple therapy options

Answer 25

**Lansoprazole + clarithromycin + amoxicillin** (metrondiazole if allergic to amoxicillin)

Question 26

Diagnosis of Helicobacter pylori infection

Answer 26

Positive urea breath test

Question 27

Example of aminosaicylates

Answer 27

Mesalazine Sulfasalazine

Question 28

What class of drug is mesalazine?

Answer 28

Aminosalicylate

Question 29

What is the use of mesalazine?

Answer 29

First line treatment of UC

Question 30

What is the mechanism of action of mesalazine?

Answer 30

Release of 5-aminosalsylic acid Anti-inflammatory effect Topic action at colon

Question 31

What are adverse drug reactions of mesalazine?

Answer 31

Nausea Dyspepsia Leukopenia (rare)

Question 32

What are important drug drug interactions of mesalazine?

Answer 32

Increased breakdown in presence of PPI due to increased pH

Question 33

Compare the use of mesalazine + sulfasalazine

Answer 33

Mesalazine - first line for UC Sulfasalazine - RA

Question 34

The half life of PPIs is only a few hours, why is acid secretion inhibited for longer than this?

Answer 34

PPIs **irreversibly** inhibit H+/K+ ATPase in parietal cells

Question 35

What drug is used first line in treatment of UC?

Answer 35

Mesalazine