9.1 - Gastrointestinal Drugs Flashcards

1
Q

What is an ulcer?

A

Defined as a rea of erosion passing through the lining of the GI wall

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2
Q

What causes stomach ulcers?

A

An imbalance between:

Aggressive factors
–> Acid, pepsin (digestive enzyme), bile (irritant), H. Pylori, NSAIDs

and Protective Factors
–> Mucus (protective layer), Pgs, bicarb (buffer), circulation

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3
Q

What is the stomach’s last line of defense against stomach acid?

A

Sufficient gastric circulation allows epithelial cells to dump acid rather than being damaged by it - this is why chronic stress can predispose someone to stomach ulcers (because blood is shunted from the GI tract)

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4
Q

What fraction of duodenal ulcers are caused by H. Pylori vs NSAIDs?

A

H. Pylori - 92%
NSAIDS - 5%

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5
Q

What fraction of gastric ulcers is caused by H. Pylori vs NSAIDs?

A

H. Pylori - 70%
NSAIDs - 25%

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6
Q

What are the two ways NSAIDs cause gastric damage?

A

Topical
–> gastric epithelial cells are damaged by absorbing an acidic drug (ASA)

Systemic
–> NSAIDs reduce synthesis of Pgs that are protective to gastric mucosa. Less of these protective PGs means less mucus, bicarb, and gastric circulation; as well as an increase in HCl secretion

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7
Q

Increased risks of NSAID related ulcers include:

A

Pts with a history of ulcer complications, who use multiple NSAIDs and/or high doses, who are on an anticoagulant, or who are 60+ years old.

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8
Q

In what two ways do antacids like magnesium hydroxide, aluminum hydroxide, and calcium carbonate help treat peptic ulcers?

A

By increasing pH (less acidic environment)
More alkaline environment means reduced activity of pepsin

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9
Q

What adverse effects do all antacids share?

A

They may reduce the absorption of certain drugs, such as digoxin, tetracycline, or ciprofloxacin

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10
Q

What are the five kinds of drugs used to treat peptic ulcers?

A
  1. Antacids
  2. Mucosal defenses
  3. H2 Antagonists
  4. PPIs
  5. Antibacterial drugs
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11
Q

What two drugs form a protective barrier over gastric mucosa?

A

Sucralfate and Bismuth Subsalicylate

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12
Q

What is an adverse effect of sucralfate?

A

Constipation

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13
Q

On top of forming a protective barrier over gastric mucosa, what does bismuth subsalicylate do for ulcers?

A

It also have bacteriostatic, antisecretory, and anti-inflammatory activities

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14
Q

What are the adverse effects of bismuth subsalicylate?

A

Can cause black tongue and feces

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15
Q

What kind of drug is misoprostol? What is its mechanism of action?

A

A PGE1 analogue
–> Synthetic PG stimulates submucosa blood flow, and increased production of bicarb and mucus
–> Also attenuates histamine-induced gastric acid secretion

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16
Q

What are the adverse effects of misoprostol?

A

Diarrhea and cramps (including contraction of the uterus - not given to pregnant women)

Used off label for cervical ripening or induction of labour.

17
Q

What pump maintains the stomach’s acidity?

A

A hydrogen-potassium ATPase

18
Q

Which things stimulate the ATPase that maintains gastric acidity?

A

Ach, Histamine (2 receptors), gastrin

Prostaglandins (PGE1) inhibits a secondary messenger after H2 stimulation.

19
Q

What kinds of drugs are cimetidine, ranitidine, famotidine, and nizatidine?

A

H2 Receptor Antagonists
–> Decrease secretion of gastric acid by parietal cells, especially at night

20
Q

What adverse effects are seen specifically with cimetidine?

A

–> Inhibits hepatic metabolism
–> Anti-androgenic effects (gynecomastia, erectile dysfunction, reduced libido, menstrual irregularities)

21
Q

What is an adverse effect of all H2 receptor antagonists?

A

Rebound acidity after discontinuation of chronic use (4+ weeks)

22
Q

What kinds of drugs are esomeprazole, omeprazole, pantoprazole, rabeprazole, dexlansoprazole and lansoprazole?

A

PPIs
–> Inhibit hydrogen-potassium ATPase

23
Q

What are the adverse effects of PPIs?

A

Well tolerated overall, however:
–> Headache and diarrhea
–> Can decrease absorption of Vit B12 and Iron
–> Long term, they increase the risk of osteoporosis or related fractural, as well as C. Diff or other GI infections

24
Q

What are the two antibiotic regimens to treat H. Pylori? How long are these regimens? What are their eradication rates?

A

Triple therapy without bismuth and quadruple therapy with bismuth

Have a duration of 7-14 days (most are 2 weeks)

Eradication rate of 85-95%

25
Q

What is the triple therapy without bismuth for H. pylori?

A

PPI (lanzoprazole)
+ Amoxicillin
+ Clarithromycin
+ Metrnidazole

26
Q

What is the quadruple therapy with bismuth for H. Pylori?

A

PPI
+ Tetracycline
+ Bismuth subsalicylate
+ Metronidazole

27
Q

What kinds of drugs are bisacodyl and sennosides? What is their mechanism of action?

A

Stimulant
–> Stimulates peristalsis and increase water and electrolytes in colon

28
Q

What kinds of drugs are psyllium and inulin? Mechanism of action?

A

Bulk-forming laxatives
–> Stimulate water retention within the stool (like dietary fiber)

29
Q

What kind of medication is docusate? Mechanism of action?

A

Surfactant
–> Alters stool consistency and facilitates penetration of water into feces

30
Q

What kinds of medication are lactulose, polyethylene glycol, and magnesium hydroxide? Mechanism of action?

A

Osmotic Laxatives
–> Poorly absorbed molecules that draw water into intestine

31
Q

What kind of laxative is mineral oil?

A

Lubrifaction
–> Can decrease absorption of fat soluble vitamins (A, D, E, K) and oral contraceptives

32
Q

What kind of drugs are methylnaltrexone and naloxegol? Mechanism of action?

A

Anti-Opioid
–> May be used to treat refractory opioid-induced constipation

33
Q

In addition to loperamide, what drugs can act as antidiarrheal agents?

A

Anticholinergic drugs, verapamil, Aluminum salts, combination of diphenoxylate and atropine.