Pharmacology of Antacids, H2 Blockers/Antagonists Flashcards

1
Q

When should antacids be taken?

A

at the onset of heartburn symptoms (effects last up to 2 hrs) because onset of action will occur within minutes.
*FASTEST ACTING

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2
Q

What are some antacids?

A
  • sodium bicarbonate (Alka-Seltzer)
  • calcium carbonate (Tums, Os-Cal)
  • magnesium + aluminum hydroxide (Gelusil, Maalox, Mylanta)
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3
Q

What should you not take calcium carbonate with?

A

tetracyclines, iron, fluoroquinolones, or itraconAZOLE (anti-fungal) bc it chelates them and decreases their effectiveness

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4
Q

What is an ADR of magnesium and an ADR of aluminum hydroxide?

A

aluminum salts= constipation, magnesium salts= diarrhea, but together they cancel each other out :)
*long term use is contraindicated in renal insufficiency

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5
Q

What are some ADRs of calcium carbonates (Tums…)?

A

metabolic alkalosis, renal insufficiency, and hypercalcemia

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6
Q

How do the Antihistamine H2 blockers work?

A

inhibit NOCTURNAL release of acid and are better suited for duodenal over gastric ulcers.

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7
Q

What are the specific antihistamine H2 blockers?

A
  • cimetiDINE
  • ranitiDINE
  • famotiDINE
  • nizatiDINE
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8
Q

What is important to know about Cimetidine?

A
  • antihistamine H2 blocker that undergoes 1st pass metabolism and BLOCKS the ANDROGEN RECEPTOR. (decreasing metabolism of estradiol, and increases prolactin levels) :(
  • absorption may be decreased by antacids
  • inhibits cytochrom P-450 enzymes
  • can cause impotency and gynecomastia in men or galactorrhea in women.
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9
Q

What is unique about Nizatidine?

A
  • H2 blocker with fastest onset, no 1st pass metabolism, and best bioavailability.
  • negligible P-450 inhibition
  • NO ANDROGEN BLOCKING :)
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10
Q

What is unique about Ranitidine (Zantac)?

A
  • H2 blocker with minimal P-450 inhibition and NO ANDROGEN BLOCKING :)
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11
Q

What is unique about Famotidine (Pepcid)?

A
  • most potent H2 blocker with negligible P-450 inhibition and NO ANDROGEN BLOCKING :)
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12
Q

What are some drug interactions involving the P-450 system with H2 blockers?

A
  • benzodiazepines, phenytoin, and warfarin
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13
Q

What are the MOST EFFECTIVE reducers of HCl secretion?

A

Proton Pump Inhibitors (PPIs) by IRREVERSIBLY inhibiting the H+/K+ ATPase

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14
Q

When are PPIs used?

A

Zollinger-Ellison syndrome (gastrin-secreting tumors), gastric/duodenal ulcers, and gastroesophageal reflux disease (GERD).

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15
Q

What are the specific PPIs?

A
  • OmePRAZOLE (Prilosec)= only one that causes P450 inhibition.
  • EsomePRAZOLE (Nexium)
  • LansoPRAZOLE
  • PantoPRAZOLE
  • RaberPRAZOLE
  • all should be taken on empty stomach and all undergo 1st pass metabolism.
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16
Q

What are some ADRs of PPIs?

A

headache, rash, HYPERGASTRINEMIA (due to gastrin trying to stimulate more H+ production from negative feedback), and colonic cell hyperplasia.

17
Q

Are PPIs superior to H2 blockers with H. pylori infection, hemorrhagic ulcers/bleeding, and when pt is using NSAIDS?

A

YES

18
Q

When are H2 blockers better?

A

safer in pregnancy (except cimetidine), and have lower incidence of ADRs

19
Q

What is Sucralfate?

A
  • cytoprotective agent that interacts with HCl to form a VISCOUS PASTE that binds to proteins in ulcers or erosions.
  • claims to stimulate mucosal PG synthesis
  • think of it like a band-aid for the stomach
20
Q

What must you remember with sucralfate regarding antacids, H2 blockers and PPIs?

A

administer 2 hrs prior to any of these drugs because it will inhibit the absorption of them.

21
Q

What is Misoprostol?

A

PGE1 analog the increases mucus/NO/HCO3- secretion, cell proliferation, and decreases acid secretion (via EP3 receptor).

22
Q

What are some important points about Misoprostol?

A
  • must be taken 3-4x daily
  • contraindicated in pregancy
  • cramps are common side effect
  • not used frequently
23
Q

What is Bismuth subsalicylate (Pepto-Bismol)

A
  • colloidal preparation of bismuth (heavy metal, not absorbed) and salicylate (absorbed). Bismuth binds mucus glycoproteins, coats/protects GI, and increases mucus/HCO3- secretion, PG synthesis, and decreases intestinal secretions.
  • indicated for dyspepsia (indigestion) and acute diarrhea.
  • also has some bacteriocidal properties to H. pylori
24
Q

How do we treat Helicobacter pylori?

A

triple therapy of:

  • PPI
  • Clarithromycin
  • amoxicillin or metronidazole
  • using a PPI will increase the pH of the stomach, thus increasing the effectiveness of antibiotics (especially amoxicillin).
25
Q

How do we treat GERD?

A
  • lifestyle modification
  • prokinetic agents
  • acid suppression
  • antireflux surgery
26
Q

What are the prokinetic drugs given for GERD?

A
  • Metoclopramide= blocks enteric GI presynaptic dopamine D2 receptors, thus increasing ACh activity (cholinomimetic), which increases upper GI tone/motility. Also has anti-emetic effects
  • Bethanechol= muscarinic (M3) actions, which increases lower esophageal sphincter pressure and GI motility (rarely used)
  • Erythromycin (antibiotic)= motilin agonist
27
Q

What other drugs besides prokinetic drugs are given for GERD?

A

acid suppressors (H2 blockers, PPIs)

28
Q

What surgical approach can be taken for overproduction of stomach acid?

A

vagotomy to prevent vagal ACh secretion and thus acid production.