252 Pharmacology - Acid Controlling Drugs Flashcards

1
Q

Which glands of the stomach are the largest in number and of primary importance when discussing acid control?

A

Gastric glands

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2
Q

What is the function of parietal cells?

A
  • Produce and secrete hydrochloric acid
  • Primary site of action for many of the drugs used to treat acid-related disorders
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3
Q

What do chief cells do?

A
  • Secrete pepsinogen, a proenzyme
  • Pepsinogen becomes pepsin when activated by exposure to acid.
  • Pepsin breaks down proteins (proteolytic).
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4
Q

What are the purposes of mucous cells?

A
  • Mucus-secreting cells (surface epithelial cells)
  • Provide a protective mucus coat
  • Protect against self-digestion by hydrochloric acid and digestive enzymes
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5
Q

When is hydrochloric acid secreted?

A
  • Secreted by parietal cells when stimulated by food, caffeine, chocolate, and alcohol
  • Secretion also stimulated by
    • Large fatty meals
    • Emotional stress
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6
Q

What pH does HCl keep the stomach at?

A

˜Maintains stomach at pH of 1 to 4

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7
Q

What does HCl do?

A

Acidity aids in the proper digestion of food and defenses against microbial infection via the gastrointestinal tract

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8
Q

What does triple therapy for H. pylori involve?

A

Triple therapy includes a 7- to 14-day course of a proton pump inhibitor (PPI) and the antibiotics clarithromycin and either amoxicillin or metronidazole or quadruple therapy of a PPI, bismuth subsalicylate, and the antibiotics tetracycline and metronidazole.

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9
Q

What are the characteristics of stress-related mucosal damage in hospitalized patients?

A
  • Gastrointestinal lesions are a common finding in Critical Care Unit patients, especially within the first 24 hours after admission.
  • Factors include decreased blood flow, mucosal ischemia, hypoperfusion, and reperfusion injury.
  • Nasogastric tubes and ventilators predispose patients to gastrointestinal bleeding.
  • A histamine receptor–blocking drug or a PPI are given for prevention.
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10
Q

What are the classes of acid controlling drugs?

A
  • Antacids
  • H2 antagonists
  • PPIs
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11
Q

How do antacids help with acid controlling?

A
  • Basic compounds used to neutralize stomach acid
  • Salts of aluminum, magnesium, calcium, or sodium bicarbonate, or all of these
  • Many antacid preparations also contain the antiflatulent (antigas) drug simethicone.
  • Many aluminum- and calcium-based formulations also include magnesium, which not only contributes to the acid-neutralizing capacity but also counteracts the constipating effects of aluminum and calcium.
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12
Q

Antacids that may lead to the development of kidney stones and increased gastric acid secretion.

A

Calcium antacids

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13
Q

What kind of antacid must be avoided in patients with renal failure?

A

Antacids containing magnesium

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14
Q

Which antacid is a highly soluble antacid form with a quick onset but a short duration of action.

A

Sodium bicarbonate

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15
Q

What is the mechanism of action of antacids?

A
  • Do not prevent the overproduction of acid but instead help to neutralize acid secretions
  • Promote gastric mucosal defensive mechanisms
  • Stimulate secretion of:
    • Mucus: protective barrier against hydrochloric acid
    • Bicarbonate: helps buffer acidic properties of hydrochloric acid
    • Prostaglandins: prevent activation of proton pump
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16
Q

What is the drug effect of antacids?

A
  • Reduction of pain and reflux associated with acid-related disorders
  • Raising the gastric pH 1 point (1.3 to 2.3) neutralizes 90% of the gastric acid.
  • Reducing acidity reduces pain as a result of:
    • Base-mediated inhibition of the protein-digesting ability of pepsin
    • Increase in the resistance of the stomach lining to irritation
    • Increase in the tone of the cardiac sphincter
17
Q

What are the indications for antacids?

A
  • Acute relief of symptoms associated with peptic ulcer, gastritis, gastric hyperacidity, and heartburn
18
Q

What contraindications are there for antacids?

A
  • Known allergy to a specific drug product
  • Severe renal failure or electrolyte disturbances: potential toxic accumulation of electrolytes in the antacids themselves
  • Gastrointestinal obstruction: Antacids may stimulate gastrointestinal motility when they are undesirable because of the presence of an obstructive process requiring surgical intervention.
19
Q

What OTC antacid formulations are available?

A
  • Capsules and tablets
  • Powders
  • Chewable tablets
  • Suspensions
  • Effervescent granules and tablets
20
Q

List the types of antacids.

A
  • Aluminum hydroxide
  • Magnesium hydroxide
  • simethicone
  • Combination aluminum hydroxide and magnesium hydroxide contain a local anaesthetic (Mucaine®).
21
Q

What are the characteristics and examples of aluminum salts?

A
  • Have constipating effects
  • Often used with magnesium to counteract constipation
  • Often recommended for patients with renal disease (more easily excreted)
  • Examples
    • Combination products (aluminum and magnesium): Antacid Plus®, Diovol®, Gelusil®, Maalox®, Multiaction®
22
Q

What are the characteristics and examples of magnesium salts?

A
  • Commonly cause diarrhea; usually used with other drugs to counteract this effect
  • Dangerous when used with renal failure; the failing kidney cannot excrete extra magnesium, resulting in accumulation
    • Magnesium hydroxide and mineral oil (Magnolox®)
23
Q

What are the characteristics and examples of calcium salts?

A
  • Many forms but carbonate is most common
  • May cause constipation, kidney stones
  • Also not recommended for patients with renal disease—may accumulate to toxic levels
  • Long duration of acid action—may cause increased gastric acid secretion (hyperacidity rebound)
  • Often advertised as an extra source of dietary calcium
    • Example: calcium carbonate and simethicone (Maalox, Rolaids®)
24
Q

What are the characteristics of sodium bicarbonate as an antacid?

A
  • Highly soluble
  • Buffers the acidic properties of hydrochloric acid
  • Quick onset but short duration
  • May cause metabolic alkalosis
  • Sodium content may cause problems in patients with heart failure, hypertension, or renal insufficiency.
25
Q

What are the adverse effects of the various antacids?

A
  • Minimal and depend on the compound used
  • Overuse: metabolic alkalosis
  • Aluminum and calcium: constipation
  • Magnesium: diarrhea
  • Calcium: kidney stones, rebound hyperacidity
  • Calcium carbonate: produces gas and belching; often combined with simethicone
26
Q

What are the drug interactions for antacids?

A
  • Adsorption of other drugs to antacids
    • Reduces the ability of the other drug to be absorbed into the body
  • Chelation
    • Chemical binding, or inactivation, of another drug
    • Produces insoluble complexes
    • Result: reduced drug absorption
  • Increased stomach pH
    • Increased absorption of basic drugs
    • Decreased absorption of acidic drugs
  • Increased urinary pH
    • Increased excretion of acidic drugs
    • Decreased excretion of basic drugs