GI Drugs

Question 1

Antacids example

Answer 1

Gaviscon

Question 2

Antacids MOA

Answer 2

• Compound containing alginate and 1+ antacid
• Alginate: increase viscosity of stomach contents to reduce reflux
• Antacids: buffer stomach acids
• After reacting with stomach contents, form a floating ‘raft’ which separates gastric contents from GOJ preventing mucosal damage

Question 3

Antacids indications

Answer 3

1. Ulcers
2. Non-ulcer dyspepsia
3. GORD

Question 4

Antacids contraindications

Answer 4

• Aluminium / magnesium hydroxide should not be given to patients with hypophosphatemia
• Sodium bicarbonate avoided for patients on low salt diet

Question 5

Antacids side effects

Answer 5

• constipation / diarrhoea
• flatulence
• stomach cramps
• nausea

Question 6

Antacids interactions

Answer 6

Divalent cations in compound alginates bind to other drugs and reduce their absorption: ACEi, Abx, bisphosphonates, digoxin, levothyroxine, PPIs.
Doses should be taken at different times - 2 hour gap

Question 7

Antacids patient info

Answer 7

Action prolonged if durg taken 1-3 hours after food

Question 8

H2 receptor agonists examples

Answer 8

Ranitidine

Question 9

H2 receptor agonists indications

Answer 9

1. Peptic ulcer disease: treatment and prevention, although PPIs more effective
2. GORD / dyspepsia: symptomatic relief

Question 10

H2 receptor agonists MOA

Answer 10

Histamine from parietal cells binds to H2 receptor
Activates proton pump on parietal cell which secretes H+ into lumen (and draws K+ into cell)
Blockade of H2 = decreased acid

Question 11

H2 receptor agonists contraindications

Answer 11

Dose reduction in renal impairment

Question 12

H2 receptor agonists side effects

Answer 12

• Generally well tolerated

- Most common: bowel disturbance, headache, dizziness

Question 13

PPIs examples

Answer 13

Lansoprazole, Omeprazole Patoprazole

Question 14

PPIs indications

Answer 14

1. Prevention and treatment of peptic ulcer disease including NSAID-associated ulcers
2. Symptomatic relief of dyspepsia and GORD
3. Eradication of H. Pylori in combination with antibiotics

Question 15

PPIs MOA

Answer 15

• Irreversibly inhibit H+/K+ ATPase in gastric parietal cells.
• This reduces gastric acid secretion
• More effective than H2 receptor agonists

Question 16

PPIs administration

Answer 16

Oral

Injectable

Question 17

PPIs contraindications

Answer 17

-Risk of osteoporosis: can increase fracture risk

Question 18

PPIs side effects

Answer 18

• GI upset
• Headache
• Reduce host defence against infection - increased risk of C. diff
• Prolonged treatment can cause hypomagnesia - can lead to ventricular arrhythmias

Question 19

PPIs interactions

Answer 19

cP450 inhibitor

Reduce anti-platelet effect of clopidogrel by decreasing its activation by cP450

Question 20

PPIs patient info

Answer 20

• Take with food or on empty stomach

- Best taken in morning

Question 21

Anti-motility agents examples

Answer 21

Loperamide, codeine phosphate

Question 22

Anti-motility agents indications

Answer 22

1. Diarrhoea: symptomatic treatment - IBS or viral gastroenteritis

Question 23

Anti-motility agents MOA

Answer 23

• Opioid which doesn’t penetrate the CNS so has no analgesic effects
• Agonist of the mu-opioid receptors in the GIT, which increases non-propulsive contractions of the gut smooth muscle
• Reduces peristaltic contractions
• Bowel content slowed . + sphincter tone increased
• Slower gut transit allows more time for water absorption which hardens stool

Question 24

Anti-motility agents administration

Answer 24

Oral capsule, tablet, syrup

Question 25

Anti-motility agents contraindications

Answer 25

1. Acute ulcerative colitis: inhibition of peristalsis may increase of megacolon and perforation 2. Clostridium difficile colitis: inc. diarrhoea associated with broad-spec antibiotic use 3. Acute bloody diarrhoea: this may signify bacterial infection

Question 26

Anti-motility agents side effects

Answer 26

- Constipation - Abdominal cramping - Flatulence

Question 27

Laxatives examples

Answer 27

Senna, lactulose, macrogol

Question 28

Laxatives indications

Answer 28

1. Constipation and faecal impaction 2. Bowel preparation prior to surgery 3. Hepatic encephalopathy

Question 29

Laxatives MOA

Answer 29

- Based on osmotically active substances are not digested / absorbed are left in lumen, and therefore hold water in the stool, maintaining its volume and stimulating peristalsis - Lactulose increases gut transit rate and acidifies the stool which inhibits ammonia producing bacteria

Question 30

Laxatives administration

Answer 30

Oral | Enema

Question 31

Laxatives contraindications

Answer 31

1. Intestinal obstruction: risk of perforation | 2. Heart failure, ascites, electrolyte disturbance: enemas can cause significant fluid shift

Question 32

Laxatives side effects

Answer 32

- Flatulence, nausea and abdominal cramps - Diarrhoea - Phosphate enemas can cause local irritation and electrolyte disturbance

Question 33

Laxatives interactions

Answer 33

May enhance effects of warfarin

Question 34

Aminosalicylates examples

Answer 34

Mesalazine, sulfasalazine

Question 35

Aminosalicylates indications

Answer 35

1. Ulcerative colitis: mesalazine 1st line | 2. Rheumatoid arthritis: sulfasalazine acts as DMARD as part of combination therapy

Question 36

Aminosalicylates MOA

Answer 36

Ulcerative colitis: Release 5-aminosalicylic acid, which is anti-inflammatory and immunosuppressive.

Question 37

Aminosalicylates administration

Answer 37

Oral: coated in acid resistant substance so released further along gut Foam enema Suppository

Question 38

Aminosalicylates contraindications

Answer 38

Aspirin hypersensitivity (aspirin is salicylate)

Question 39

Aminosalicylates side effects

Answer 39

GI upset (nausea, dyspepsia) Headache Rare but serious blood abnormalities: leucopenia, thrombocytopenia Renal impairment Oligospermia Hypersensitivity: rash, fever, liver damage

Question 40

Aminosalicylates interactions

Answer 40

Drugs which alter gut pH e.g. PPIs - may cause premature breakdown

Question 41

Anti-emetics examples

Answer 41

Metoclopramide, Domperidone

Question 42

Anti-emetics indiactions

Answer 42

Prophylaxis and treatment of nausea and vomiting, particularly in context of reduced gut motility

Question 43

Anti-emetics MOA

Answer 43

- D2-receptor antagonists - D2 is main receptor in chemoreceptor trigger one of medulla, the area responsible for sensing emetogenic substances in blood e.g. drugs - Dopamine is important NET in gut: promotes relaxation of stomach and lower oesophageal sphincter, inhibits gastroduodenal coordination - D2 receptor agonists have prokinetic effect - promote gastric emptying - Effective in nausea and vomiting due to chemoreceptor trigger zone stimulation and reduced gut motility

Question 44

Anti-emetics adinistration

Answer 44

IV injections

Question 45

Anti-emetics contraindications

Answer 45

1. GI obstruction | 2. Young - increased risk of extra-pyramidal side effects

Question 46

Anti-emetics side effects:

Answer 46

- Diarrhoea | - Extra-pyramidal ssyndromes: dystonic reaction

Question 47

Anti-emetics interactions

Answer 47

1. Antipsychotics: increased risk of extra-pyramidal side effects 2. Parkinson's dopaminergic agents: antagonises