31. Gastrointestinal and Antiemetic Drugs

Question 1

What are the main two causes of peptic ulcer disease?

Answer 1

Infection with Helicobacter pylori and use of NSAIDs.

Question 2

What are the approaches to treating peptic ulcer disease?

Answer 2

Eradicating H. pylori infection, reduce gastric acid secretion with PPIs or H2 antagonists, protect gastric mucosa from damage.

Question 3

What antimicrobials are used in H pylori eradication in peptic ulcer disease?

Answer 3

Amoxicillin, clarithromycin, metronidazole, tetracycline.

Question 4

What H2-histamine receptor blockers are used in peptic ulcer disease management?

Answer 4

Cimetidine, famotidine, nizatidine, ranitidine.

Question 5

What PPIs are used in peptic ulcer disease management?

Answer 5

Omeprazole, lansoprazole, esomeprazole.

Question 6

Name a prostaglandin used in peptic ulcer disease management.

Answer 6

Misoprostol.

Question 7

Name an antimuscarinic agent used in peptic ulcer disease management.

Answer 7

Dicyclomine.

Question 8

What antacids are used in peptic ulcer disease management?

Answer 8

Aluminium hydroxide, calcium carbonate, magnesium hydroxide, sodium bicarbonate.

Question 9

Which mucosal protective agents can be used in peptic ulcer disease management?

Answer 9

Bismuth subslicylate, sucralfate.

Question 10

How is H pylori infection diagnosed?

Answer 10

Endoscopic biopsy of gastric mucosa, serology, or urea breath tests.

Question 11

What is the triple therapy approach to H pylori eradication?

Answer 11

PPI + 2 x antibiotics (depends on hospital’s guidelines - amoxicillin + clarithromycin).

Question 12

Which hormones stimulate gastric acid secretion?

Answer 12

Acetylcholine, histamine, and gastrin.

Question 13

How do ACh, histamine, and gastrin stimulate gastric acid secretion?

Answer 13

Receptor mediated binding activates protein kinases which stimulate the H+/K+/ATPase to secrete hydrogen ions in exchange for K+ into the lumen of the stomach.

Question 14

What is the action of H2 receptor antagonists?

Answer 14

Competitive antagonists of histamine, this is fully reversible.

Question 15

What are the uses of H2 receptor antagonists?

Answer 15

Peptic ulcers, acute stress ulcers, GORD.

Question 16

What are the ADRs of H2 antagonists?

Answer 16

Endocrine effects of cimetidine - gynaechomastia, galactorrhoea. CNS effects - confusion, altered mentation. Reduce efficacy of drugs that require an acidic environment for absorption.

Question 17

What is the mechanism of action of PPIs?

Answer 17

Binds to H+/K+/ATPase so suppresses the secretion of hydrogen ions into gastric lumen.

Question 18

What is Zollinger-Ellison syndrome?

Answer 18

Gastrin-producing tumour causes hypersecretion of HCl.

Question 19

What is another benefit of PPIs other than reducing acid production?

Answer 19

Reduces risk of bleeding from ulcers caused by aspirin and other NSAIDs.

Question 20

What are the ADRs of PPIs?

Answer 20

Inhibit CYP2C19 => DDIs. Increased risk of fractures (particularly if used for >1 year), low vitamin B12 and calcium, diarrhoea, Clostridium difficile, hypomagnesaemia, increased incidence of pneumonia.

Question 21

How can prostaglandins improve peptic ulcer disease?

Answer 21

They inhibit secretion of acid and stimulate secretion of mucus and bicarbonate. If there’s a deficiency of prostaglandins in peptic ulcers, this balance can be corrected.

Question 22

What are the key ADRs of prostaglandins?

Answer 22

Diarrhoea and nausea.

Question 23

What are antacids?

Answer 23

Weak bases tat react with gastric acid to form water and a salt to diminish gastric acidity. Also reduces pepsin activity.

Question 24

What are antacids used for?

Answer 24

Symptomatic relief of peptic ulcer disease and GORD, healing of duodenal ulcers.

Question 25

What are the ADRs of antacids?

Answer 25

Constipation or diarrhoea depending on drug, absorption problems in patients with renal problems.

Question 26

What are the cytoprotective properties of antacids?

Answer 26

Enhance mucosal protective protection mechanisms so prevent mucosal injury, reduce inflammation, and heal existing ulcers.

Question 27

What are the two brainstem sites that have key roles in the vomiting reflex pathway?

Answer 27

Chemoreceptor trigger zone in postrema, vomiting centre in lateral reticular formation of medulla.

Question 28

What is the role of the chemoreceptor trigger zone in the postrema?

Answer 28

Responds to chemical stimuli in blood or CSF.

Question 29

What is the role of the vomiting centre in the lateral reticular formation of the medulla?

Answer 29

Coordinates the motor mechanisms of vomiting and responds to afferent input from brainstem and cortical structures.

Question 30

What can be used in motion sickness?

Answer 30

Loperamide, an antimotility drug.

Question 31

What are the major factors in diarrhoea?

Answer 31

Increased motility in the GI tract and decreased absorption of fluid.

Question 32

What are the drug classes used to treat diarrhoea?

Answer 32

Antimotility drugs, adsorbents, agents that modfiy fluid and electrolyte transport.

Question 33

Name an antimotility agent used in diarrhoea.

Answer 33

Loperamide.

Question 34

What is the action of loperamide on the gut in diarrhoea?

Answer 34

Opioid-like actions to activate presynaptic opioid receptors in enteric nervous system to inhibit ACh release and decrease peristalsis.

Question 35

What are the methods for treating constipation?

Answer 35

Irritants and stimulants, bulk laxatives, saline and osmotic laxatives, stool softeners, lubricant laxatives, chloride channel activators.

Question 36

What is the action of senna?

Answer 36

Stimulant laxative - causes evacuation of the bowels within 8-10 hours and causes water and electrolyte secretion into bowel.

Question 37

What is the action of bulk laxatives?

Answer 37

They form gels in the large intestine causing water retention and intestinal distension so increase peristaltic activity.

Question 38

How do osmotic laxatives work?

Answer 38

They hold water in the intestine by osmosis. This distends the bowel and increases intestinal activity, so produces defecation in a few hours.

Question 39

Name an osmotic laxative.

Answer 39

Lactulose.

Question 40

``` 45yo women has persistent heartburn and an unpleasant, acid-like taste in her mouth. She is suspected to have GORD so she is advised to eat smaller meals, not eat just before bed, and to prop her head up at night. Two weeks later her symptoms are still concerning for her. What should be prescribed? A. anatacid, e.g. aluminium hydroxide. B. dicyclomine C. antianxiety agent, e.g. alprazolam. D. esomeprazole ```

Answer 40

D. esomeprazole - PPI to reduce acid production and promote healing.

Question 41

``` A couple are celebrating their 40th wedding anniversary and go to Peru. They have had past experience while travelling that mean they'd like an agent for diarrhoea. Which should be given? A. omeprazole. B. loperamide. C. famotidine. D. lorazepam. ```

Answer 41

B. loperamide - antidiarrhoeal, unlike the rest of the list. (A is a PPI, C is an H2 antagonist, and D is a sedative and anxiolytic).

Question 42

``` 27yo woman is 34 weeks pregnant and on bed rest, she is mildly constipated. What should be recommended? A. castor oil B. docusate C. mineral oil D. loperamide ```

Answer 42

B. docusate - safe in pregnancy (castor oil isn't as it can cause uterine contractions, mineral oil isn't used in bedridden patients as aspiration risk and loperamide is an anti-diarrhoetic).

Question 43

``` Which of the following can cause discolouration of the tongue? A. amoxicillin. B. omeprazole. C. bismuth compounds. D. lubiprostone. ```

Answer 43

C. bismuth compounds - black discolouration.

Question 44

``` Which of the following is not generally well tolerated for treatment of constipation? A. castor oil B. methylcellulose C. polyethylene glycol D. docusate ```

Answer 44

A. castor oil - can cause severe cramping.

Question 45

``` An elderly woman with recent Hx of MI has occasional heartburn. She is on aspirin, clopidogrel, simvastatin, metoprolol, and lisinopril. Which should be avoided? A. calcium citrate B. famotidine C. omeprazole D. ranitidine E. calcium carbonate ```

Answer 45

C. omeprazole - it can reduce efficacy of clopidogrel as it inhibits conversion to active form.

Question 46

``` Which of the following GI drug is contraindicated in pregnancy? A. calcium carbonate B. famotidine C. lansoprazole D. misoprostol ```

Answer 46

D. misoprostol - stimulates uterine contractions.