GI drugs:

Question 1

Domperidone/metoclopramide

Answer 1

acts on postrema on floor of 4th ventricle and increases the rate of gastric emptying.

Question 2

5-HT antagonists (ondansetron)

Answer 2

acts on floor of the 4th ventricle and acts against vagal nerves.

Question 3

what else can be used as an anti-emetic drug?

Answer 3

mAchr antagonist, H1 antagonists.

Question 4

bulk (isphagula husk)

Answer 4

insoluble substance that distends gut and leads to peristalsis and gut motility.

Question 5

faecal softeners (glycerol)

Answer 5

lubricate and soften stool.

Question 6

osmotic (phosphate enemas)

Answer 6

causes water retention which distends bowl and increases motility.

Question 7

irritant/stimulant (castor oil)

Answer 7

excitation of sensory nerve endings which leads to water and electrolyte retention and hence peristalsis.

Question 8

opiate analgesics (as GI drugs)

Answer 8

increase anal tone and reduce motility by blocking enteric opioid receptors, but don’t cross the BBB.

Question 9

bulk forming

Answer 9

small amount of faecal fluid regulates bowel habit and prevents constipation or diarrhoea.

Question 10

mebeverine

Answer 10

relieves intestinal muscle spasms. Used in IBS.

Question 11

PPIs (lansoprazole)

Answer 11

bind to active proton pumps and irreversibly destroys the pump.

Question 12

H2 antagonists (ranitidine)

Answer 12

block stimulatory effects of histamine on parietal cells.

Question 13

antacids (gaviscon)

Answer 13

neutralise stomach acids.