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Gastro > Drugs for peptic ulcer disease > Flashcards

Drugs for peptic ulcer disease Flashcards

1
Q

Rank potency of gastric drugs from highest to lowest

A
  1. Proton pump inhibitors
  2. H2 receptor antagonist
  3. Antacids - neutralise acidity with base
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2
Q

Types of antacids

A

NaHCO3
CaCO3
Mg(OH)2
Al(OH)3

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3
Q

Antacids MOA

A
  • weak base, neutralise gastric acid
  • reduce gastric acidity, DOES NOT prevent gastric acid production

potency
- NaHCO3 > CaCO3 > Mg(OH)2 > Al(OH)3

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4
Q

Indication for antacid

A
  • non prescription remedy for HEART BURN, DYSPEPSIA
  • large, frequent doses required
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5
Q

Why do some antacids contain simethicone

A

simethicone: anti-foaming agent
- ease release of gas (CO2) within GI tract via burping/ flatulence

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6
Q

Na+, Ca2+ antacids adverse effects

A
  • Na+ antacids: fluid retention, hypertension, CHF
  • Ca2+ antacids: hypercalcemia, rebound acid secretion (after discontinuing medicine)

common to both:
- metabolic alkalosis

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7
Q

HCO3-, CO3- antacids adverse effects

A
  • belching, flatulence from CO2 gas formation
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8
Q

Mg2+, Al3+ antacids adverse effects

A
  • Mg2+ antacids: osmotic diarrhoea
  • Al3+ antacids: constipation
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9
Q

antacids contraindication

A
  • avoid LT use in RENAL INSUFFICIENCY
  • do not take within 2 HOURS of other medication
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10
Q

H2 receptor antagonist examples

A

FAMOTIDINE (most potent), ranitidine, cimetidine (least potent)

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11
Q

H2 receptor antagonists MOA

A
  • competitive inhibitor of H2 receptors, suppress acid secretion by PARIETAL cells
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12
Q

H2 receptor antagonist efficacy

A
  • inhibit 60-70% of total gastric acid secretion
  • inhibit NOCTURNAL acid secretion
  • little effect on meal induced acid secretion (meals trigger acid secretion from other mediators - gastrin, AChE)
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13
Q

when is the most appropriate time to take famotidine

A
  • at night before sleeping -> inhibit NOCTURNAL acid secretion
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14
Q

therapeutic index of H2 antagonists

A
  • high therapeutic index -> relatively safe
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15
Q

H2 antagonists adverse effects

A

famotidine & ranitidine:
- headache, nausea, dry mouth
- (RARE, severe): tachycardia, blood dyscrasia, blurred vision, musculoskeletal pain

cimetidine:
- headache, nausea, diarrhea
- ANTI ANDROGENIC -> gynaecomastia (men); galactorrhoea (women)

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16
Q

PPI (proton pump inhibitor) examples

A

Omeprazole, Esomeprazole (S-isomer of omeprazole)

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17
Q

omeprazole MOA

A
  • inhibit H+/K+/ATPase (proton pump) in PARIETAL cells
  • IRREVERSIBLE block
  • some antimicrobial activity (against H pylori, but insufficient)
18
Q

why do PPI contain enteric coating

A
  • protect against activation by stomach acidity before absorption (active drug very poorly absorbed)
19
Q

how is PPI activated

A
  • enteric coating protects drug from stomach -> prodrug is released and absorbed in small intestines
  • prodrug has good bioavailability in blood -> eventually enters PARIETAL CELL CANALICULUS -> protonated & activated
  • drug forms IRREVERSIBLE covalent disulfide bonds with proton pump in parietal cell
20
Q

can PPI be taken with food?

A

NO. bioavailability is decreased 50% by food
- give on EMPTY stomach (usually 1 hr before breakfast)

21
Q

Why must meals be taken 1 hour after PPI (and not longer?)

A
  • PPIs inhibit active pumps (not resting pumps) -> pumps active when food is present in stomach
  • PPIs have SHORT t1/2 (1-2hr) -> must give food soon after ingestion so PPI is still present in bloodstream to take effect
22
Q

PPI dosage

A

irreversible blockage -> 24hours block -> ONCE DAILY

23
Q

PPI adverse effects

A
  • headache, nausea, flatulence, diarrhoea, dizziness, rash
  • increase risk of C. difficile infection
  • hypomagnesemia

(RARE): acute interstitial nephritis, chronic kidney disease, SLE

24
Q

Gastric mucosal protection drug examples

A
  • Sucralfate
  • Bismuth compounds
  • Misoprostol
25
Q

gastric mucosal protection drug indications

A
  • PREEXISTING peptic ulcers (cannot be treated by gastric acid secretion drugs)
26
Q

sucralfate MOA

A
  • Negatively charged sucrose sulphate binds to positively
    charged proteins at ulcer crater forming a viscous,
    tenacious gel -> prevents further acid attack
    – Stimulates mucosal PG -> increase bicarbonate and mucus secretion
27
Q

sucralfate systemic effects

A
  • highly insoluble -> NO systemic effects
28
Q

how is sucralfate administered

A
  • on empty stomach (1hr before food) -> prevent binding to +ve charges on food
29
Q

sucralfate adverse effects

A
  • constipation (contain Al(OH)3)
  • impair absorption of other drugs
30
Q

bismuth compounds MOA

A
  • forms a protective layer protecting ulcers from acid and pepsin
    – stimulates mucus and bicarbonate secretion
    – directly anti-microbial activity against H. pylori
31
Q

bismuth compounds adverse effects

A
  • harmless blackening of stool, reversible blackening of tongue
  • ONLY short term use (prolonged use -> bismuth toxicity, encephlopathy)
  • AVOID in renal insufficiency
32
Q

Misoprostol MOA

A
  • PGE1 analogue (mimic endogenous PG)
  • Binds to PGE2 receptors (EP1-4)
    – Low dose (cytoprotective): promotes bicarbonate and
    mucus secretion, enhances mucosal blood flow
    – High dose (antisecretory): inhibits gastric acid secretion
33
Q

Indications of misoprostol

A
  • prevent NSAID induced peptic ulcers
34
Q

Misoprostol adverse effects

A
  • Abdominal pain
    – Diarrhoea
    – Abortion (uterine contraction)
    – Bone pain and hyperostosis (excessive bone growth)
35
Q

what is the triple therapy for H pylori infection

A
  • clarithromycin
  • amoxicillin or metronidazole
  • PPI (omeprazole/ esomeprazole)

(2 antibiotics + 1 PPI), 7-14 days

36
Q

why are 2 antibiotics used in triple therapy against H pylori

A
  • H pylori becomes resistant to metronidazole & clarithromycin when given alone
37
Q

PPI MOA in triple therapy

A
  • increase gastric acid pH (H pylori multiplies better at higher pH)
  • antibiotics work best when H pylori is MULTIPLYING

after completion of triple therapy, PPI is continued to ensure complete healing:
– 4-8 weeks for duodenal ulcers
– 8-12 weeks for gastric ulcers

38
Q

administration of antibiotic in triple therapy

A
  • twice a day
  • with/ after food within 1 hour (reduce GI effects)
39
Q

administration of PPI

A
  • twice a day
  • after 2 hours fasting, + 30min-1hr before food
40
Q

second line quadruple therapy drugs

A

– 1 Bismuth + 2 antibiotics + 1 PPI or H2 antagonist (10-14 days

Gastro (20 decks)

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