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SP1- Week5 > Drugs That Reduce Gastric Acid > Flashcards

Drugs That Reduce Gastric Acid Flashcards

1
Q

Stimulatory:
1. Histamine
2. Gastrin
3. Acetylcholine

A

Inhibitory:
1. PGE2
2. PGI2
3. Somatostatin

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2
Q

Histamine:

Released by..
Increased by …
Acts how

A

 Released by enterochromaffin-like cells (ECL)  Further increased by gastrin and acetylcholine
 Histamine acts in a paracrine fashion on
parietal cell H2 receptors
 Increasing intracellular cAMP  Responsive to histamine concentrations below
threshold required for vascular H1
receptor activation

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3
Q

CLINICAL INDICATIONS FOR REDUCING ACID SECRETION

A

-Peptic ulceration (both duodenal and gastric)
* H. Pylori infxn
- GORD
* gastric acid damages oesophagus
- Zollinger- Ellison syndrome
* rare gastrin- producing tumor
- NSAIDS
* COX-2 inhibitors may offer an advantage by causing less GI-related adverse effects

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4
Q

THERAPEUTIC STRATEGIES

A

H2 receptor antagonists
 Proton pump inhibitors
 Antacids
 Alginates
 H. pylori eradication
 Cytoprotective agents

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5
Q

HISTAMINE H2 RECEPTOR ANTAGONISTS
MoA

A

 Major breakthrough in the treatment of gastric ulcers
 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

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6
Q

. HISTAMINE H2 RECEPTOR ANTAGONISTS
, Beneficial Effects

A

Promote healing of gastric and duodenal ulcers
-Relapses likely to follow after cessation of treatment

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7
Q

Histamine receptor antagonists
Examples

A

Cimetidine, nizatidine, famoditine
Less effective than proton pump inhibitors (PPIs)

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8
Q

Adverse effects

A

 Diarrhoea
 Dizziness
 Headache
 Hypergastrinaemia

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9
Q

Cimetidine Adverse effects

A

 Gynaecomastia in men and rarely, a decrease in sexual function
 Probably caused by a modest affinity for androgen receptors
 CYP450 inhibitor
 Potentiates effects of a range of drugs e.g. oral anticoagulants and tricyclic antidepressants

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10
Q

Clinical uses for Histamine receptor antagonist

A

• Peptic ulcer disease: treatment
and prevention of gastric and
duodenal ulcers (including
NSAID-associated ulcers)
• GORD and dyspepsia

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11
Q

First line tx

A

Proton pump inhibitors

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12
Q

PROTON PUMP INHIBITORS
Prototypical drug + other examples

A

Prototypical drug: Omeprazole

Other PPIs
 Esomeprazole
 Lansoprazole
 Pantoprazole
 Rabeprazole

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13
Q

PPI MoA

A

—Irreversibly inhibits the proton pump
• Basal and stimulated gastric acid secretion are reduced
— Weak base
• Accumulates in the acid environment of the canaliculi of the stimulated parietal cell where it is activated
• Administration: 30 minutes before food
• Specific effect on parietal cells

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14
Q

Adverse effects are uncommon

A
  • Headache
  • Diarrhoea
  • Rebound hypergastrinemia (problem when stopping tx)
  • Hypomagnesemia
  • Increased bone fracture risk
  • Increased susceptibility to infections (e.g.
    C difficile)
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15
Q

CLINICAL USES
Of PPI

A

• 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

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16
Q

Antacids INDICATIONS+MoA

A

 Treat the symptoms of excessive gastric acid secretion
 Directly neutralize acid
 May produce healing of duodenal ulcers
 Calcium salts induce gastrin secretion

17
Q

Antacids CI, careful

A

 Some preparations contain high concentrations of sodium
 Should not be given to patients on a sodium-restricted diet
 May cause changes in acidity and thus pharmacokinetic interactions with other drugs
 Recommended to take them at least 2 hours apart from other drugs

18
Q

Antacids commonly used

A

 Magnesium (Mg) salts cause diarrhea
 Aluminum (Al) salts cause constipation
 Mixtures of Mg/Al can preserve normal bowel function

19
Q

Antacids examples

A
  1. Aluminium hydroxide
  2. Calcium carbonate
  3. Magnesium hydroxide
20
Q

Aluminium hydroxide AE

A

• Constipation
• Hypophosphatemia
• Muscle weakness
• Osteodystrophy

21
Q

Calcium carbonate AE

A

• Hypercalcaemia
(milk alkali syndrome)
• Rebound acidity
• Chelate and decrease effectiveness of
other drugs

22
Q

Magnesium hydroxide

A

• Diarrhoea hydroxide
• Hyporeflexia • Hypotension • Cardiac arrest

23
Q

Aliginates MoA

A

 Sometimes combined with
antacids

 May increase viscosity and
adherence of mucus to the oesophageal mucosa
 Forming a protective barrier

24
Q

Alginates Clinical uses

A

• Most often taken as compound
preparations containing an alginate with
one or more antacids for:
• GORD: for symptomatic relief of
heartburn
• Dyspepsia: for short-term relief of
indigestion

25
Q

TREATMENT OF HELICOBACTOR PYLORI INFECTION

A

 Causative factor in gastric and duodenal ulcers

H. pylori eradication
 Rapid and long-term healing of ulcers
 Routine practice to test for the organism
 If positive 1- or 2-week regimen of ‘triple therapy’
•PPI + 2 antibiotics: Amoxicillin (or metronidazole) and clarithromycin
• Other combinations are also used
 Bismuth-containing preparations sometimes added
• Quadruple therapy (in patients with macrolide resistance): PPI; Bismuth; Metronidazole; Tetracycline

 Quadruple therapy may alternatively include 3 antibiotics + PPI

26
Q

-DRUGS THAT PROTECT THE MUCOSA

A

-Cytoprotective agents
-Bismuth chelate

27
Q

Cytoprotective agents
MoA

A

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

28
Q

Bismuth chelate
MoA

A

 Adjunct in H. pylori treatment
 Toxic effects on the bacillus
 May also prevent its adherence to the mucosa or inhibit its bacterial proteolytic enzymes
 May also have other mucosa-protecting actions

29
Q

Bismuth chelate
Clinical use

A

'’Clinical Use: widely used as an over-the-counter remedy
for mild GI symptoms and in quadruple therapy for H.pylori
eradication

30
Q

Bismuth AE

A

 Nausea  Vomiting  Blackening of the tongue and faeces

 In renal impairment may cause encephalopathy
• Salicylate component
Therefore, pts with aspirin allergy shouldn’t take this

31
Q

MISOPROSTOL clinical uses

A

 Stable analogue of PGE 1
 Promotes the healing of ulcers
 Prevents gastric damage due to chronic use of NSAIDs
—- Now PPIs used

More 3rd line

32
Q

MISOPROSTOL MoA

A

 Exerts a direct action on the ECL cell
 Possibly on parietal cells as well
 Inhibits basal and stimulated secretion of gastric acid
 Increases mucosal blood flow
 Augments the secretion of mucus and
bicarbonate

33
Q

MISOPROSTOL AE

A

 Diarrhea
 Abdominal cramps
 Uterine contractions can also occur
-Should not be given during pregnancy for
this indication
(Given to induce abortion)

34
Q

GERD (Mild/ intermittent)

A

1st line - Antacids, H2RA
Alternative - PPIs

35
Q

GERD (severe)

A

1st line - PPIs
Alternative - H2 RA (step down)

36
Q

Pregnancy

A
  1. Antacids
  2. H2RA, PPIs
37
Q

H. Pylori eradication

A
  1. Triple therapy
    (Amoxicillin or metronidazole
    Clarithromycin; PPI)
  2. Quadruple therapy (in pts. W/ macrolide resistance): PPI; bismuth; metronidazole; tetracycline
38
Q

NSAID prophylaxis

A
  1. PPIs
  2. MISOPROSTOL, H2RA
39
Q

Zollinger Ellison Syndrome

A
  1. PPIS
  2. Somatostatin analogues

SP1- Week5 (1 decks)

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