GI Pharmacology

Question 1

What are the three main areas of GI pharmacology?

Answer 1

Drugs that suppress gastric acid
Drugs that affect gut motility and secretions
Drug treatment for inflammatory bowel diseases
Laxatives

Question 2

What are the main two conditions that are treated by acid-suppressing drugs?

Answer 2

Acid reflux (GORD)
Peptic ulcer disease

Question 3

Give three classes of drugs for acid suppression

Answer 3

H2 antagonists
Proton pump inhibitors
Antacids

Question 4

How do H2 antagonists work?

Answer 4

Block the H2 (histamine) receptors
- histamine released from ECL cells in the stomach stimulates parietal cells to produce stomach acid, therefore blocking the H2 receptors decreases acid production

Question 5

Give four examples of H2 antagonists

Answer 5

Cimetidine
Famotidine
Nicatidine
Ranitidine

Question 6

How do PPIs work? Give an example of a PPI

Answer 6

Reduce the number of hydrogen ions (protons) that are pumped into the stomach lumen

• this reduces the amount of stomach acid being produced
  e. g. omeprazole

Question 7

How do antacids work?

Answer 7

Directly neutralise hydrogen ions in the stomach lumen

- some also coat the surface of the oesophagus to protect against stomach acid

Question 8

Give some common ingredients in antacids

Answer 8

aluminium hydroxide
magnesium carbonate
magnesium trisilicate

Question 9

What conditions/symptoms are treated by drugs that affect gut motility?

Answer 9

Vomiting
Abdominal pain
Diarrhoea
Constipation
Irritable bowel syndrome

Question 10

What do prokinetic agents do? What are they used to treat?

Answer 10

Increase gut motility and gastric emptying

Treat gastroparesis, GORD

Question 11

Give two examples of prokinetic agents and describe how they work

Answer 11

Metoclopramide, Domperidone
Dopamine antagonists
Involves parasympathetic nervous system control of smooth muscle and sphincter tone (via ACh)

Question 12

Give two examples of drugs that decrease gastric motility and describe how they work

Answer 12

Loperamide (immodium), Opiates
Work via opiate receptors in GI tract to decrease ACh release
Decrease smooth muscle contraction
Increase anal sphincter tone

Question 13

Which class of drugs can be useful in IBS? 
Give an example
Describe the various mechanisms involved

Answer 13

Anti-spasmodics, e.g. Buscopan
1. Anti-cholinergic muscarinic antagonists (hyoscine buscopan, mebeverine)
inhibit smooth muscle constriction in the gut wall, producing muscle relaxation and reduction spasm.
2. Direct smooth muscle relaxants
3. Calcium-channel blockers (peppermint oil) reduce calcium required for smooth muscle contraction

Question 14

Describe the effect of fibre on stool constistency

Answer 14

Increase fibre to treat constipation

Decrease fibre to treat diarrhoea

Question 15

Describe how laxatives work and give four types (and an example for each type)

Answer 15

Either by increasing bulk of faeces or by drawing fluid into the gut

• Bulk e.g. Isphagula
• Osmotic e.g. Lactulose
• Stimulant e.g. Senna
• Softeners e.g. Arachis oil

Question 16

Describe the potential issues with laxative use

Answer 16

Do not give if there may be an obstruction
Consider lifestyle changes first
Route of administration: oral or rectal
Need for other measures, e.g. osmotic laxatives require adequate fluid intake in order to work
Ensure patient is actually in need of them
Misuse

Question 17

What classes of drugs are used to treat inflammatory bowel disease?

Answer 17

Aminosalicyclates
Corticosteroids
Immunosuppressants
Biologics

Question 18

Describe the use of aminosalicyclates in treating IBD

Answer 18

Anti-inflammatory
Metabolised in the liver
Oral or rectal administration

Question 19

Give two examples of aminosalicyclates

Answer 19

Mesalazine, Olsalazine

Question 20

Describe the side-effects and potential adverse effects related to aminosalicyclates

Answer 20

Nausea is common
Potential to cause GI upset, blood dyscrasia, renal impairment
Chemically similar to salicyclates which some patients are allergic to - must be avoided if this is the case
Use with caution (or not at all) in patients with pre-existing renal impairment

Question 21

Describe the use to corticosteroids in treating IBD

Answer 21

Anti-inflammatory
Given orally, IV or rectally
Often used to settle acute attacks

Question 22

Why must you be cautious with long term use of steroids?

Answer 22

Risk of Addisonian crisis if steroids are withdrawn too abruptly

Question 23

Describe the concerns/contraindications associated with steroid use

Answer 23

Osteoporosis
Cushingoid features including weight gain, DM, HT
Increased susceptibility to infection
Addisonian crisis with abrupt withdrawal

Question 24

Describe the use of immunosuppressants in the treatment of IBD and give an example

Answer 24

E.g. Azathioprine
Prevents the formation of purines required for DNA synthesis, so reduces immune cell proliferation
Good for when reducing dose of steroids

Question 25

What are the risks associated with using immunosuppressants?

Answer 25

Adverse effects: bone marrow suppression, azathioprine hypersensitivity, organ damage
Numerous drug interactions

Question 26

Which organs are most at risk of being damaged by immunosuppressant use?

Answer 26

Lung
Liver
Pancreas

Question 27

What are biologics and what are they used for? Give an example

Answer 27

Anti-TNFa antibodies
E.g. infliximab
Mouse-human chimeric antibody to TNFa
Used to treat IBD, psoriasis and rheumatoid arthritis

Question 28

How to biologics work?

Answer 28

Prevents action of TNFa, a key cytokine in inflammatory response
Addresses inflammatory response but not underlying disease processes

Question 29

Give three contraindications for infliximab

Answer 29

Current TB or other serious infection
Multiple sclerosis
Pregnancy/breast feeding

Question 30

What are the potential adverse effects of Infliximab?

Answer 30

Risk of infection, particularly TB
Infusion reaction - fever, itch
Anaemia, thrombocytopenia, neutropenia
Malignancy
Possible demyelination

Question 31

Give five other examples of biologics (aside from infliximab)

Answer 31

Certolizumab
Adalimumab
Natalizumab
Golimumab
Vedolizumab

Question 32

Give two drugs that affect biliary secretions

Answer 32

Cholestyramine - reduces bilirubin

Ursodeoxycholic Acid - dissolves/prevents gallstones

Question 33

Describe the effects of cholestyramine

Answer 33

Used to treat pruritis from biliary cause
Reduces bile salts by binding with them in the gut and hen excreting as an insoluble complex
May affect absorption of other drugs - must be taken separately
May affect soluble vitamin absorption so may decrease vitamin K level
- this affects clotting so must be careful if a patient is also on warfarin

Question 34

Describe the uses/effects of ursodeoxycholic acid

Answer 34

used to treat gallstones and primary biliary cirrhosis
inhibits an enzyme involved in the formation of cholesterol, altering amount in bile and slowly dissolving non-calcified stones

Question 35

Define pharmacodynamics

Answer 35

How a drug affects an organism

Question 36

Define pharmacokinetics

Answer 36

How an organism affects a drug

Question 37

What are the main effects of antibiotic-induced changes to the gut flora?

Answer 37

Loss of oral contraceptive pill (OCP) activity
Reduced vitamin K absorption (increased prothrombin time)
Overgrowth of pathogenic bacteria (e.g. Clostridium difficile)

Question 38

Which scoring system is used to classify prognosis in chronic liver disease and cirrhosis? What is its role in prescribing?

Answer 38

Child-Pugh score
Classify patients as high or low risk (Class A, B, C)
Helps to decide strength of treatment needed and extend of effect on ADME of other drugs (particularly warfarin and other anticoagulants)

Question 39

Give an example of a commonly used drug that can injure the liver

Answer 39

Paracetamol