Gastrointestinal drugs

Question 1

What are the four categories of GI drugs?

Answer 1

Antacids, H2 receptor antagonists, cytoprotective drugs, PPI’s

Question 2

What is the mechanism of action of antacids?

Answer 2

Neutralise HCl, raise gastric pH, protect gastric epithelial cells and duodenal lining

Question 3

What are examples of antacids?

Answer 3

Magnesium hydroxide/carbonate, aluminium hydroxide

Question 4

What are the adverse effects of antacids?

Answer 4

diarrhoea (Mg), constipation (Al), Al also assoc with increased risk of alzheimers, delays or reduces absorption of other drugs - separate by at least 2 hours.

Question 5

What are H2 receptor antagonists used for?

Answer 5

short term use for PUD or GORD

Question 6

Name two H2 receptor antagonists

Answer 6

Cimetidine, ranitidine

Question 7

How do H2 receptor antagonists work?

Answer 7

they block histamine from stimulating the H2 receptors on parietal cells, inhibiting secretion of gastric acid

Question 8

what are the ADR of H2 receptor antagonists?

Answer 8

gastrointestinal or CNS. Not recommended for elderly. Also inhibits metabolism of other drugs via CYP450 pathway, increasing adverse effects and toxicities.

Question 9

What are two kinds of cytoprotective drugs?

Answer 9

Synthetic prostaglandin E1 (eg misoprosol); sulfated sucrose and Aluminium hydroxide eg sucralfate

Question 10

What conditions are prostaglandin analogues used for?

Answer 10

peptic ulcers and prevention of gastric ulcers assoc with NSAID use

Question 11

how do prostaglandin analogues work

Answer 11

Synthetic prostaglandins are cytoprotective at low dose (prostaglandins protect gastric mucosa from injury). Increase bicarbonate and mucous production, stimulate gastric mucosal blood flow, strengthen mucosal barrier against H+ diffusion

Question 12

what are the ADR from prostaglandin analogues

Answer 12

cardiovascular, gastrointestins, causes miscarriage (contraindicated in pregnancy)

Question 13

What is sucralfate used for

Answer 13

short term treatment for peptic ulcers

Question 14

how does sucralfate work

Answer 14

forms a gel in presence of acid
forms a protective barrier to ulcer from gastric acid
stimulates protective prostaglandins and mucous

Question 15

What are the ADR of sulfated sucrose

Answer 15

gastrointestinal. Antacids decrease effectiveness of them. They decrease absorption of some Abiotix.

Question 16

When are proton pump inhibitors used?

Answer 16

For GORD and short term treatment of PUD (8-12 wks)

Question 17

How do proton pump inhibitors work?

Answer 17

they inhibit the H+/K+ ATPase pump (ie proton pump) on the secretory surface of the parietal cells, thereby inhibiting secretion of HCl. Reduce amt HCl secreted, reduce erosive quality of refluxate, reduce oesophogeal damage.

Question 18

What are two examples of PPIs?

Answer 18

Pantoprazole, Omeprazole

Question 19

what are the ADR of PPIs?

Answer 19

no alcohol, GI (nausea, vomiting, diarrhoea), increase release of gastrin (causes cancer in rats but no evidence in humans), reduces the absorption of drugs that require an acidic environment.