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Adv Pharm 1 > GI (pt 2/5) Antacids, H2 Blockers > Flashcards

GI (pt 2/5) Antacids, H2 Blockers Flashcards

1
Q

What are the 4 goals of Antacid Therapy?

A

1) Reduction of intragastric acidity
-Neutralize the pH of stomach contents already there
-Decrease further production of gastric acid
-Stomach pH is between 1-3; Antacid therapy increases pH to 4-5
2) Mucosal protection:
-Reinforce the lining of the stomach
-Allow ulcerations to heal
-Prevent further bleeding/re-bleeding
3) Stimulation of GI motility and tighten the LES
-Keep gastric contents in the stomach
4) Prevention and treatment of nausea and vomiting, regardless of etiology
-PONV
-Block the central receptors in the Chemoreceptor Trigger Zone and the Vomiting Center

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2
Q

What 3 things stimulate the secretion of HCl?

A

-Ach
-Gastrin
-Histamine

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3
Q

Gastric secretions can be up to ___ L/day.

A

2

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4
Q

pH in the stomach is?

A

1.0 - 3.5

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5
Q

pH of a molecule of HCl acid is?

A

0.8

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6
Q

An increase in gastric pH should _______ the chance of aspiration pneumonitis.

A

An increase in gastric pH should decrease the chance of aspiration pneumonitis

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7
Q

Inhalation of gastric fluid causes what?

A

Aspiration pneumonitis.
-Particulate or liquid stomach contents in the lung hurts the trachea, lung tissue and inhibits gas exchange.

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8
Q

What is the pH of saliva?

A

6.7

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9
Q

What is the pH of the small intestine?

A

6.5-7.5

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10
Q

What are antacids?

A

Drugs that neutralize the acid of gastric contents.
-Were the primary agent for acid-peptic disorders until the release of H2 antagonists and PPIs.
-Nonprescription remedies for the treatment of dyspepsia and acid-peptic disorders.
-Effects last 1-2 hours

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11
Q

Weak bases that react with HCl to form a salt and water.
-Reduce gastric acidity.

A

Antacids (!!)

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12
Q

Antacids are ___ bases that react with HCl to form ____ and ____.

A

Antacids are weak bases that react with HCl to form a salt and water. (!! blue box)
-Reduce gastric acidity

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13
Q

What is dyspepsia?

A

Indigestion
-Upper abdominal discomfort described as a burning sensation, bloating or gassiness or feeling of nausea

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14
Q

What is Pepsin?

A

An endogenous chemical that increases gastric production.

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15
Q

What physiologic effects happen if the stomach pH is increased to >4.5 ?

A

-Inactivate pepsin
-Increase gastric motility
-Increase lower esophageal sphincter tone

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16
Q

Why are Particulate Antacids NOT used for pre-op?

A

!!! Blue Box:
If aspirated, can cause inflammation and granulation tissue.
-Produce a foreign body reaction if aspirated
-Airway mucosa inflammation
-Granulation tissue forms around the particulates leading to a lung infection
-Clinical reports suggest that the inhalation of particulates is as bad as inhalation of acid.

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17
Q

What are the 3 examples of Particulate Antacids?

A

1) Sodium Bicarbonate (Alka Seltzer)
2) Calcium Carbonate (Tums)
3) Magnesium Hydroxide and Aluminum Hydroxide (Mylanta/Maalox)

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18
Q

What is the example drug of Sodium Bicarbonate (Particulate Antacid)?

A

Alka Seltzer

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19
Q

What is the MOA of Sodium Bicarbonate Antacids (Alka Seltzer)?

A

Reacts with HCL to produce carbon dioxide & sodium chloride.
-Belching (from the CO2)
-Metabolic alkalosis

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20
Q

What is the example drug of Calcium Carbonate (Particulate Antacid)?

A

Tums

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21
Q

What is the MOA of Calcium Carbonate Antacids (Tums)?

A

Reacts with HCL to form carbon dioxide & calcium chloride (CaCl2).
-Belching (from the CO2)
-Metabolic alkalosis

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22
Q

What is the example drug of Magnesium Hydroxide & Aluminum Hydroxide Particulate Antacids?

A

Mylanta & Maalox

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22
Q

What is the MOA of Magnesium Hydroxide & Aluminum Hydroxide Antacids (Mylanta & Maalox)?

A

Reacts slowly with HCL to form magnesium chloride or aluminum chloride and water.

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23
Q

What is the unique side effect associated with Magnesium Hydroxide?

A

Mg = must go
Diarrhea

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24
Q

What is important to know about Antacids and interactions with other drugs?

A

All antacids may affect the absorption of other medications by binding the drug or increasing intragastric pH altering the drug’s solubility.
-Antacids should not be given within 2 hours of some antibiotics, antifungals (Can change absorption of these other drugs).

25
Q

What are particulates?

A

Minute, separate particles.
-Clinical reports suggest that the inhalation of particulates is as bad as inhalation of acid

26
Q

What is the example drug of the NON-Particulate Antacids?

A

Sodium Citrate.
Bicitra ®
Polycitra ®

27
Q

What is the formula for Bicitra? and what pH does it increase the stomach to?

A

Na citrate + citric acid. pH = 4.5

28
Q

What is the formula for Polycitra? and what pH does it increase the stomach to?

A

Na citrate + K citrate + citric acid. pH = 5.2

29
Q

Compare Non-Particulate Antacids (Sodium Citrate) to Particulate Antacids.

A

Non-Particulates:
-Faster and better mix with gastric contents
-More rapid onset of action
-Prevents injury to lungs/trachea if aspiration risk

30
Q

What is important to know about Na Citrate compared to Bicitra or Polycitra?

A

pH = 8.4, so VERY effective increase of pH, but it tastes TERRIBLE so not palpable. That’s why Bicitra or Polycitra are used, as they don’t make the pH as high, so they taste better, but are not as clinically effective.

31
Q

Citrate is rapidly metabolized to _____, causing the possibility of _____ and _____ alkalosis.

A

Citrate is rapidly metabolized to bicarbonate, causing the possibility of systemic and urine alkalosis.

32
Q

What is the dosing/administration facts regarding Non-Particulate Antacids (Na Citrate)?

A

-Dose: 15-30 mL
-Administer 15-30 min before induction
-Refrigerate if possible and take it like a shot.

33
Q

What are H2 Receptor Antagonists?

A

Drugs that produce selective & reversible inhibition of H2 receptor-mediated secretion of gastric acid in the GI tract.
-Decrease the volume of gastric secretion and the concentration of pepsin

34
Q

What is the MOA of H2 Receptor Antagonists?

A

Competitive inhibition at the parietal cell H2 receptor and suppression of basal and meal-stimulated acid secretion.

35
Q

____ were the most commonly prescribed drugs for gastric issues until H Pylori’s role was identified in peptic ulcer disease and the advent of proton pump inhibitors.

A

H2 Receptor Antagonists

36
Q

Why are H2 Receptor Antagonists used pre-op?

A

-Decrease production of gastric acid
-Decrease chance of aspiration pneumonitis.

37
Q

What patient conditions are predisposed to aspiration and thus should receive pre-op H2 Receptor Antagonist administration?

A

-GERD
-Obesity
-Full Stomach
-Trauma

38
Q

Antagonism of the H2 Receptor causes what physiologic effects?

A

-The Histamine released from ECL cells, by gastrin or vagal stimulation is blocked from binding to the parietal H2 receptor
-Direct stimulation of the parietal cell by gastrin or Ach has a decreased effect on acid secretion in the presence of H2 Antagonists

39
Q

What are the 4 example H2 Receptor Antagonists?

A

Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pepcid)
Nizatidine (Axid)

40
Q

H2 Receptor Antagonists inhibit ____ - ___% of total 24 hour acid secretion. (!!! Blue Box!!)

A

H2 Receptor Antagonists inhibit 60%-70% of total 24-hour acid secretion.

41
Q

What are the Pharmacokinetics associated with H2 Receptor Antagonists?

A

-All are rapidly absorbed from the intestine
-Cimetidine, ranitidine, and famotidine ALL undergo first-pass hepatic metabolism = 50% bioavailability
-DOA: depending on drug, 5-12 hrs (BID administration)
-Clearance: hepatic metabolism, glomerular filtration, & renal tubular secretion*
-More impact on Night Histamine secretion.

42
Q

What is important to know when administering a H2 Receptor Antagonist to a patient with renal or hepatic insufficiency?

A

H2 Receptor Antagonists are hepatic metabolism, and cleared via glomerular filtration and renal tubular secretion.
-Dose reduction is required with moderate to severe renal & hepatic insufficiency

43
Q

Why do H2 Receptor Antagonists have a greater impact on nocturnal acid secretion?

A

Nocturnal acid secretion is largely histamine dependent, whereas meal-stimulated secretion involves histamine, Ach, and gastrin.

44
Q

Prescription doses of H2 Receptor Antagonists maintain greater than ___% inhibition for 10 hours.

A

Prescription doses of H2 Receptor Antagonists maintain greater than 50% inhibition for 10 hours.

45
Q

What time of day is Histamine secretion increased?

A

Histamine secretion is more at night to help with regulation of hormones.
-In the afternoon, histamine is at its lowest.
-Colds get worse at night.

46
Q

Why do you need to infuse H2 Receptor Antagonists slowly, over 15-30 minutes? (!Blue Box!)

A

It is better to infuse H2 Blockers over 15-30 minutes due to possible effect on cardiac H2-receptors.
-Can produce bradycardia and hypotension.

47
Q

H2 Receptor Antagonists can cause negative ____ and _____, reducing HR. They are also shown to ______ BP in CHF patients.

A

H2 Receptor Antagonists can cause negative inotropy and chronotropy, reducing HR. They are also shown to decrease BP in CHF patients.

48
Q

Which H2 Receptor Antagonist can be very irritating to the veins?

A

Pepcid (famotidine)

49
Q

Why would an ICU patient be on a continuous H2 Receptor Antagonist drip (like Zantac)?

A

For stress ulcer prevention.
-Can keep it running in the OR if you have a line.
-Has minimal to no Side Effects.

50
Q

What are the adverse effects associated with H2 Receptor Antagonists?

A

-Diarrhea
-Headache
-Fatigue
-Myalgias
-Constipation
-Mental Status Changes (Cimetidine)
-Gynecomastia/Impotence/Galactorrhea (Cimetidine)

51
Q

Overall, side effects associated with H2 Receptor Antagonists occur in less than ___% of patients = these are safe drugs.

A

Overall, side effects associated with H2 Receptor Antagonists occur in less than 3% of patients = these are safe drugs.

52
Q

Some studies suggest that H2 Blockers and Proton Pump Inhibitors may ________ the risk of nosocomial pneumonia in critically ill patients.

A

Some studies suggest that H2 Blockers and Proton Pump Inhibitors may increase the risk of nosocomial pneumonia in critically ill patients.

Lack of acid in stomach = risk of infection due to pathogens

53
Q

What is important to know regarding pregnancy and H2 Receptor Antagonists?

A

They cross the placenta and are excreted in breast milk.
-No known teratogenic effects but recommended not to be administered to pregnant women unless absolutely necessary
-May affect nursing infant

54
Q

Which populations should you avoid the use of Cimetidine due to the mental status changes?

A

Critically ill or elderly with renal/hepatic dysfunction.
-Can cause confusion

55
Q

How does Cimetidine cause gynecomastia, impotence, or galactorrhea?

A

Inhibits binding of DHT to Androgen Receptors; inhibits breakdown of estradiol.

Rare less than 1%

56
Q

What populations do you avoid the use of Cimetidine in due to the risk of gynecomastia, impotence, or galactorrhea?

A

Avoid in people with hormone issues, cancers.

57
Q

Which H2 Receptor Antagonist INHIBITS CYP450, CYP3A4, and crosses the BBB?

A

Cimetidine

58
Q

What are the effects associated with Cimetidine because it crosses the BBB?

A

Histamine neurotransmitter in CNS- reports of confusion, hallucinations, delayed awakening (avoid in elderly)

59
Q

Ranitidine binds ____ -____ times less than _______.

A

Ranitidine binds 4-10 times less than Cimetidine.
-Negligible binding from Nizatidine and Famotidine.

60
Q

Cimetidine would prolong the 1/2 lives of what kinds of drugs? Give examples.

A

Drugs metabolized by the CYP450/CYP3A4 pathways.
-Dilantin, Tegretol, Coumadin, Valium, most opioids.

61
Q

H2 Receptor Antagonists (except for Famotidine) ____ the first-pass metabolism of ____, especially in women. Clinical Significance is unknown (! Blue Box!)

A

H2 Receptor Antagonists (except for Famotidine) INHIBIT the first-pass metabolism of Ethanol, especially in women. Clinical significance is unknown.

Adv Pharm 1 (28 decks)

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