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Pharmacology Exam 1 > 13 - GI Pharmacology I > Flashcards

13 - GI Pharmacology I Flashcards

1
Q

What are all the products which regulate gastric secretions?

A
  • Hydrochloric acid (HCl)
  • Intrinsic factor (IF)
  • Pepsinogen
  • Bicarbonate, mucus
  • Histamine
  • Gastrin
  • Acetylcholine (ACh)
  • Somatostatin
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2
Q

What is the source and function of HCl in the stomach?

A
  • Parietal cell

- Protein digestion, sterilization, nutrient absorption

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3
Q

What is the source and function of IF in the stomach?

A
  • Parietal cell

- Vitamin B12 absorption

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4
Q

What is the source and function of pepsinogen in the stomach?

A
  • Chief cell

- Protein digestion

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5
Q

What is the source and function of mucus and bicarbonate in the stomach?

A
  • Superficial epithelial/neck cells

- Gastroprotection

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6
Q

What is the source and function of histamine in the stomach?

A
  • ECL cells

- Promote HCl secretion

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7
Q

What is the source and function of gastrin in the stomach?

A
  • G cell

- Promote HCl secretion

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8
Q

What is the source and function of ACh in the stomach?

A
  • Nerve cells

- Promote mucus, bicarb and HCl secretion

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9
Q

What is the source and function of somatostatin in the stomach?

A
  • D cells

- Suppress HCl secretion

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10
Q

How does gastrin act both directly and indirectly?

A

Endocrine function

  • Directly: stimulate parietal cells to increase activity of the H+-K+-APase
  • Indirectly: inducing the release of histamine by ECL cells
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11
Q

How does acetylcholine act both directly and indirectly

A

Neurocrine

  • Directly: stimulation of pariental cells
  • Indirectly: stimulation of ECL cells resulting in the release of histamine (histamine then stimulates H+-K+-ATPase)
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12
Q

Describe the protection of the gastric mucosa

A

Prostaglandins
- Prostaglandins (PGE2) decrease H+-K+-ATPase activity which pumps H+ into the stomach

PGE2 and ACh
- Prostaglandins and acetylcholine promote mucus and bicarb secretion from gastric epithelial cells

Somatostatin
- Decreases acid secretion by inhibiting the release of gastrin from G cells, inhibiting the release of histamine from ECL cells and inhibiting H+-K+-ATPase activity

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13
Q

What is the goal of antacids?

A
  • Neutralize gastric acid
  • Reach a pH of 4
  • Possibly stimulate secretion of prostaglandins for protection
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14
Q

What are the four antacids you need to know?

A

1 - Sodium bicarbonate
2 - Calcium carbonate
3 - Magnesium hydroxide
4 - Aluminum hydroxide

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15
Q

What is the duration of action for all antacids?

A

Very short acting - 1-2 hours

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16
Q

What is the rate of reactivity for the antacids (how quick after you take them do they start working)?

A

1 - Sodium bicarbonate (FAST)
2 - Calcium carbonate (MODERATE)
3 - Magnesium hydroxide (SLOW)
4 - Aluminum hydroxide (SLOW)

This can be clinically beneficial because you can take two at once and by the time one stops working the next one starts

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17
Q

What are common adverse effects of all antacids?

A
  • Reduce drug bioavailability (if you’re taking a different drug orally, it will break it down too so you don’t get the drug’s effect)
  • Enteric infection (because there isn’t a harsh enough environment to kill the bacteria)
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18
Q

What are the specific adverse effects of sodium bicarbonate?

A
  • Metabolic alkalosis
  • Excessive sodium absorption and fluid retention
  • Gas and bloating
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19
Q

What are the specific adverse effects of calcium carbonate?

A
  • Acid rebound (pH goes up via a feedback mechanism)

- Gas and bloating

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20
Q

What are the specific adverse effects of magnesium hydroxide?

A

Osmotic diarrhea

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21
Q

What are the specific adverse effects of aluminum hydroxide?

A

Constipation

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22
Q

What are antacids commonly used to treat?

A
  • Gastroesophageal reflux disease (GERD)
  • Peptic ulcers
  • Dyspepsia

When treating peptic ulcers, antacids are just as effective as H2-receptor antagonists, but have lower compliance because you have to take them so frequently

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23
Q

What are H2-receptor antagonists?

A
  • Highly selective competitive inhibitors of the histamine H2-receptor in the stomach
  • Block the release of gastrin and acetylcholine-induced acid secretion
  • Readily absorbed by the gut, but can be IV or IM if needed
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24
Q

What are the four H2-receptor antagonists you need to know?

A

1 - Cimetidine
2 - Ranitidine
3 - Nizatidine
4 - Famotidine

25
Q

What is the duration of action of all H2-receptor antagonists?

A 
10 hours (prescription strength)
6 hours (OTC strength)
26
Q

What are common adverse effects of all H2-receptor antagonists?

A

Headache

Safe drugs*

27
Q

What are some of the adverse effects specific to cimetidine?

A
  • CNS effects (confusion, hallucinations, agitation)
  • Endocrine effects (inhibition of androgen receptors, inhibition of estradiol metabolism, increase in prolactin levels)
  • Liver effects (inhibition of hepatic CYP metabolism)
28
Q

What are H2-receptor antagonists used to treat?

A
  • Dyspepsia
  • Gastritis
  • GERD
  • Peptic ulcers

The “heal rate” with these drugs (which is similar to antacids) is 50% for GERD and 80% for peptic ulcers

29
Q

What do proton pump inhibitors (PPIs) do?

A
  • Block the final common pathway in acid secretion by the gastric mucosa - H+-K+-ATPase in parietal cells
30
Q

What does it mean to say that PPIs are prodrugs?

A

They require low pH for activation

31
Q

Describe the absorption and drug action of PPIs

A
  • They are in a protective coat so they don’t get activated in the stomach because they would never make it through the mucosa layer to work
  • They instead travel to small intestine, get absorbed there, then get to the stomach via the blood stream
  • They are then taken up by parietal cells and they irreversibly bind to and inhibit the H+-K+-ATPase
32
Q

When are PPIs most effective?

A

Maximum effect in acid reduction is obtained after 3 to 4 days of dosing and a single dose is effective for approximately 24 hours

33
Q

How does it work for the drug to irreversibly bind? What happens when you go off the drug?

A

Reactivation of the H+-K+-ATPase requires new protein synthesis of the pump.

34
Q

What are the five PPIs that you need to know?

A
  • Omeprazole
  • Lansoprazole
  • Raberprazole
  • Esomeprazole
  • Pantoprazole
35
Q

What is the duration of action of PPIs?

A

24 hours

Remember it takes 3-4 days for the dose to reach its max effect

36
Q

What are the common adverse effects of all PPIs?

A

Overall they are extremely safe

  • Decreased drug bioavailability (other drugs)
  • Diarrhea, headache, abdominal pain (only 1-5%)
37
Q

What are the less common adverse effects of PPIs?

A
  • Decreased nutrient absorption (vitamin B12, iron, calcium, zinc)
  • Enteric and respiratory infection
38
Q

What are the therapeutic uses of PPIs?

A
  • Most effective inhibitors of acid secretion
  • Heal rate of 90% for GERD and peptic ulcers
  • Used for H Pylori-associated ulcers, NSAID ulcers, dyspepsia, gastritis and hypersecretory diseases
39
Q

What are mucosal protective agents?

A

An alternative method of reducing acid secretion by forming a physical barrier to protect ulcerated tissue and promote healing

40
Q

What are the three mucosal protective agents you need to know?

A

1 - Sucralfate
2 - Bismuth subsalicylate
3 - Misoprostol

41
Q

What is the duration of action of all mucosal protective agents?

A

6 hours

42
Q

What is the mechanism of action of sucralfate and bismuth subsalicylate?

A

Sucralfate and bismuth subsalicylate form a protective barrier over damaged tissue to prevent further tissue damage by H+ or pepsin. In addition to this physical barrier, both agents stimulate mucus and HCO3- production by the gastric mucosa through mechanisms that are not yet clear

43
Q

What is the mechanism of action for misoprostol?

A
  • Does NOT form a physical barrier
  • Instead, stimulates epithelial cells of gastric mucosa to secrete mucus and bicarb
  • Also decrease activation of H+-K+-ATPase of parietal cells
44
Q

What are the adverse effects of sucralfate?

A

Common

  • Constipation
  • Impaired drug absorption

Rare
- Take caution with renal insufficient patients

45
Q

What are the adverse effects of bismuth subsalicylate?

A

Common
- Blackening of the stool and tongue (benign)

Rare
- High doses induce salicylate toxicity

46
Q

What are the adverse effects of misoprostol?

A

Common
- Cramping and diarrhea

Rare
- Abortificient (causes an abortion in pregnant women)

47
Q

What is the clinical use of sucralfate?

A
  • Prevent stress-related bleeding in critically hospitalized patients where the suppression of acid is not ideal
48
Q

What is the clinical use of bismuth subsalicylate?

A
  • Treatment of dyspepsia

- Antibacterial action that may be useful in H pylori or traveler’s diarrhea

49
Q

What is the clinical use of misoprostol?

A
  • Prevention of NSAID-associated ulcers

However, you need to take it 3-4x/day and there are adverse effects so it is not commonly used

50
Q

How do mucosal protective agents compare to PPIs?

A

In general, the mucosal protective agents are generally 2nd line treatments to the use of the very effective PPIs

51
Q

What are H pylori?

A
  • Bacteria that colonize the lumenal surface of the stomach

- 70-90% of ulcer patients are positive for H pylori

52
Q

Does H pylori cause ulcers?

A

Unknown

- They appear to cause ulcers, however people can be positive for H pylori and not have ulvers

53
Q

What else can H pylori cause other than ulcers?

A

It has been linked to gastric lymphomas and adenocarcinomas

54
Q

How do you transmit H pylori?

A

Fecal-oral route

Mouth-to-mouth (belching)

55
Q

How do you treat H pylori ulcers?

A

Three options you need to know…

  • 1st line defense (“new triple therapy”)
  • “Old triple therapy”
  • “Quadruple therapy”

ALWAYS at least three drugs… 2 antibiotics and a PPI because they are antibiotic resistant

56
Q

What is the first line defense or the “new triple therapy”?

A
  • PPI
  • Clarithromycin (antibiotic)
  • Amoxicillin or metronidazole (antibiotic)
57
Q

What is the “old triple therapy”?

A
  • Bismuth subsalicylate
  • Tetracycline (antibiotic)
  • Metronidazole (antibiotic)
58
Q

What is the “quadruple therapy”?

A

The same as the “new triple therapy” except you also add bismuth subsalicylate (pepto bismal)

  • PPI
  • Clarithromycin (antibiotic)
  • Amoxicillin or metronidazole (antibiotic)
  • Bismuth subssalicylate

Pharmacology Exam 1 (6 decks)

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