GI 1 - Drugs reducing gastric acid

Question 1

Drugs used in the reduction of Gatric acid secreting in the GI tract

Answer 1

1) H2 receptor antagonists (2nd line)
2) Proton pump inhibitors (1st line)
3) Antacids
4) Alginates
5) H. pylori eradication
6) Cytoprotective agents

Question 2

MoA of HISTAMINE H2 RECEPTOR
ANTAGONISTS

Answer 2

• Competitively inhibit histamine actions at H2 receptors (reversible)
• Inhibit histamine- and gastrin stimulated acid secretion
• Decrease both basal and food stimulated acid secretion by 90% or more

Question 3

Histamine H2 receptor antagnoists examples

Answer 3

Cimetidine (not preferred) , nizatidine, famotidine

* -tidine

Question 4

Clinical uses of H2 receptor Antagonists

Answer 4

2nd line in the tx of Gastric/duodenal Ulcers

*less effective than PPIs

Question 5

AE of H2 receptor Antagonists

Answer 5

Unwanted effects are rare:
 Diarrhoea
 Dizziness
 Headache
 Hypergastrinaemia

*Cimetidine –> CYP450 inhibitor
- Gynaecomastia and decrease in sexual function

Question 6

MoA of PPIs

Answer 6

Weak base that protonats parietal cells -> decreases gastric acid secretion
Irreversibly inhibits the H+ pump

Question 7

PPIs Examples

Answer 7

Omeprazole,
Esomeprazole,
Lansoprazole
Pantoprazole
Rabeprazole

* -prazole

Question 8

Clinical uses of PPIs?

Answer 8

1st line
* Peptic ulcer disease: treatment and prevention of gastric and duodenal ulcers (including NSAID-associated ulcers)
* Treatment of GORD and dyspepsia
* As part of H. pylori triple/quadruple
eradication therapy
* Reduction of gastric acid secretion in Zollinger-Ellison Syndrome

Question 9

Administration of PPIs?

Answer 9

30 minutes before food

Question 10

AE of PPIs?

Answer 10

 Headache
 Diarrhoea
 Rebound hypergastrinemia (esp after stopping tx)
 Hypomagnesemia
 Increased bone fracture risk ( ↓ Ca+2 absorption)
 Increased susceptibility to infections (e.g.
C difficile)

* ↑ susceptibiltiy -> ↓ gastrin -> ↑ pH -> ↑ risk of infection

Question 11

Antacids Exmaples

Answer 11

Magnesium salts, Aluminum salts, calcium bicarbonate

Question 12

AE of Magensium salts

Answer 12

1) Diarrhoea
2) hyporeflexia,
3) hypotension,
4) cardiac arrest.

Question 13

AE of (Al) salts?

Answer 13

1) Constipation
2) hypophosphatemia,
3) muscle weakness,
4) osteodystrophy (abnormal changes in the growth and formation of bone)

Question 14

AE of calcium bicarbonate

Answer 14

1) Hypercalcaemia,
2) rebound acidity,
3) chelate and decreases effectivness of other drugs

Question 15

MoA of Mg/Al salts vs Calcium salts?

Answer 15

Mg/Al salts: Directly neutralize acid
Calcium salts: induce gastrin secretion

Question 16

Administration of Mg/Al salts

Answer 16

should be given 2h apart from other drugs
* since they may cause changed in acidity and thus pharmacokinetic interaction w/ other drugs (E.g,. reduced the absorption of beta-blockers in HF patients when taken at the same time)

Question 17

Contraindications of Mg/Al salts

Answer 17

• patients on a sodium restrited diet
• interaction w/ other drugs, therefore take them at least 2h apart from other drugs

Question 18

Clinical uses of Alginates

Answer 18

Used in combo w/ Antacids
- GORD: for symptomatic relief of heartburn
- Dyspepsia: for short-term relief of indigestion

Question 19

MoA of Alginates

Answer 19

• May increase viscosity and adherence of mucus to the
  oesophageal mucosa (prevent reflux)
• Forming a protective barrier

Question 20

————- : causative factor in gastric and duodenal ulcers

Answer 20

H.Pylori infection

Question 21

Treatment approach in the eradication of H.pylori

*Rapid and long-term healing of ulcers

Answer 21

If positive 1- or 2-week regimen of ‘triple therapy’ –> PPI + 2 antibiotics: Amoxicillin (or metronidazole) and clarithromycin ( a macrolide)

In resistant patients: quadruple therapy in (patients with macrolide resistance) (PPIs + Bismuth; metronidazole, tetracycline)

Question 22

MoA of Cytoprotective agents

Answer 22

• Enhance endogenous mucosal protection mechanisms and/or
• provide a physical barrier over the surface of the ulcer

Question 23

Clinical uses of Bismuth chelate

Answer 23

• Qurduple therpay in the eradication of H.pylori
• over-the-counter remedy for mild GI symptoms

Question 24

AE of Bismuth chelate

Answer 24

1) Nausea,
2) vomit,
3) blackening of tongue and
faeces.
*stool is sticky and smells very bad

Question 25

Contraindications of Bismuth Chelate

Answer 25

1) In renal impairment may cause encephalopathy
2) Asprine allergy

Question 26

What type of drug is Misoprostol?

Answer 26

PGE1 analogue,
–> exerts direct action on the ECL cells and maybe also on parietal cells

Question 27

MoA of Misoprostol

Answer 27

Inhibits gastric acid secretion,
increases blood flow and thus increases secretion
of mucus and bicarbonates

Question 28

Clinical uses of Misoprostol?

Answer 28

3rd line tx option
- Promotes healing of ulcers and used to
- prevent damage due to chronic use of NSAIDs.
(Now PPIs are used)

Question 29

AE of Misoprostol

Answer 29

1) Diarrhoea,
2) abdominal cramps,
3) uterine contractions (contraindicated in pregnancy)

Question 30

Contraindiactions of Misoprostol?

Answer 30

PREGNANCY (uterine contraction)