10.1 GI pharmacology

Question 1

When can ulcers be asymptomatic?

Answer 1

Chronic ulcers

Question 2

What can happen with gastric ulcers?

Answer 2

Bleeding
Perforation
Scarring
Possible obstruction - if scarring occurs around pyloric sphincter

Question 3

What causes duodenal/gastric ulcers?

Answer 3

• Acid- inability of normal [acid] to inhibit further acid
• Early gastric emptying
• Helicobacter pylori
• NSAIDs
• Smoking and alcohol may delay healing

Question 4

What are the effects of different molecules on parietal cells?

Answer 4

Stimulation:
- Acetylcholine
- Histamine
- Gastrin

Inhibition:
- Prostaglandins - NSAIDs reduce these ergo increase in production of stomach acid causing ulcers
- PGs also maintain mucosal blood flow, important for removing free H+ ions

Question 5

What do we use to reduce stomach acid?

Answer 5

Alginates and antacids
PPIs
H2 receptor antagonist

Question 6

What is an example of an alginate and antacid?

Answer 6

Gaviscon

Question 7

How do antacids and alginates work?

Answer 7

Antacids buffer stomach acid

Alginic acids increase stomach content viscosity and reduce reflux

They are often taken together as compound mixture

Question 8

What substances are alginates and antacids?

Answer 8

• Alginic acid - sodium alginate
• Antacid - aluminium hydroxide/magnesium carbonate

Question 9

What are the adverse effects of using alginates and antacids?

Answer 9

• Magnesium salts can cause diarrhoea
• Aluminium salts can cause constipation
• Gaviscon has both to avoid stop this side effect and balance each other out

Question 10

What are the contraindications and warnings of alginates and antacids?

Answer 10

• Na+ and K+ containing preparations should be used with caution in renal failure
• High sucrose in some preparations - can cause hyperglycaemia in DM pts

Question 11

What are the important drug to drug interactions with alginates and antacids?

Answer 11

Reduce absorption of many drugs so should be separated
Increased urine alkalinity can increase aspirin excretion

Can be used to treat aspirin overdose

Question 12

What are some examples of PPIs?

Answer 12

Lansoprazole
Omeprazole

-prazole suffix

Question 13

How do proton pump inhibitors work?

Answer 13

Inhibit H+K+ATPase in gastric parietal cells

Final stage in the acid production pathway

Very significant reduction in acid secretion

Question 14

What are the adverse effects of using PPIs?

Answer 14

GI disturbance
Headache, dizziness
Drowsiness/confusion

Question 15

What are the contraindications and warnings of using PPIs?

Answer 15

Masks symptoms of oesophageal cancer

Osteoporosis - fracture risk

Question 16

What are some important drug to drug interactions with PPIs?

Answer 16

Omeprazole is a CYP inhibitor - reduces clopidogrel action

PPIs can also increase effects of warfarin and phenytoin

Question 17

When are PPIs often prescribed?

Answer 17

With long-term NSAID or steroids

Pericarditis

Question 18

Give an example of an H2 receptor antagonist

Answer 18

Ranitidine

Question 19

How do H2 receptor antagonists reduce stomach acid?

Answer 19

Histamine stimulates acid production

Inhibition causes reduced acid production

Question 20

How effective are H2 receptor antagonists?

Answer 20

Only blocking histamine activation of parietal cells

Can still be stimulated by other molecules

Question 21

What are the adverse effects of H2 receptor antagonists?

Answer 21

Generally tolerated well - diarrhoea, headache

Question 22

What are the contraindications and warnings of using H2 receptor antagonists?

Answer 22

Can mask symptoms of gastro-oesophageal cancer

Renal impairment

Question 23

What are some important drug to drug interactions when using H2 receptor antagonists?

Answer 23

Few common

Reduced exposure to some antivirals and protein kinase inhibitors

Question 24

Is Ranitidine currently available?

Answer 24

No -currently removed due to containing some carcinogens

Lansoprazole first line alternative

Question 25

When should you consider a patient may be infected with helicobacter pylori?

Answer 25

All patients with duodenal or gastric ulcers that are not associated with NSAIDs or unresponsive to lifestyle PPIs and antacids

Question 26

How do we confirm infection of helicobacter pylori?

Answer 26

Urea breath test - C13 isotope use

Urea coverted to ammonia by helicobacter urease

CO2 expired

If breath contains high levels of C13 this means positive H-Pylori infection

Question 27

How is helicobacter pylori treated?

Answer 27

One week Triple therapy - PPI and two antibacterial agents

Lansoprazole + Clarithromyin + Amoxicillin or Metronidazole

Compliance with full course is important for effectiveness and minimise risk of bacterial resistance

Question 28

When is metronidazole used over amoxicillin?

Answer 28

If allergic to amoxicillin

Question 29

What is an example of an amionsalicylate?

Answer 29

Mesalazine
Sulfasalazine

-salazine suffix

Question 30

When are aminosalicyclates used?

Answer 30

First line treatment for ulcerative colitis

Question 31

How do aminosalicyclates work?

Answer 31

Release of 5-aminosalsylic acid
Topical action at the colon

Enteric coated tablets which limits gastric breakdown

Question 32

What aminosalicyclates are used in rheumatoid arthritis?

Answer 32

Sulfasalazine - has sulpha group attached so more beneficial for RA
Mesalazine no role in RA

Question 33

What are the adverse effects of aminosalicyclates?

Answer 33

GI disturbance - nausea, dyspepsia
Leukopenia - rare

Question 34

What are some warnings and contraindications when using aminosalicyclates?

Answer 34

Salicyclates are like aspirin - similar hypersensitivity can occur

Do not use in aspirin hypersensitivity

Question 35

What are some important drug to drug interactions with aminosalicylates?

Answer 35

Enteric coated tablets may break down more quickly if PPIS are being used as this increases the stomach pH