2 GI Drugs

Question 1

How do Peptic Ulcers form?

Answer 1

Mucous and bicarb normally protect stomach lining, but increased acid overcomes protective mechanisms

Increased acid can be due to:
Stress
NSAIDs
H. pylori infection

Question 2

What are the different approaches to treating peptic ulcers?

Answer 2

Decrease stomach acid
Eliminate H. pylori
Protect mucosa

Question 3

What four drugs do you use in combo to treat H. pylori infection?

Answer 3

Pepto-Bismol
Metronidazole
Clarithromycin, tetracycline, or amoxicillin
H2 blocker

Question 4

What are Antacids exactly?

Answer 4

Inorganic bases, often divalent cations

Neutralize acid by directly binding to HCl

Can be aluminum, magnesium, calcium, or sodium bicarb

Question 5

Which antacid causes diarrhea?

Answer 5

Magnesium

Question 6

Which antacid causes constipation?

Answer 6

Aluminum

Aluminum and magnesium often combined to cancel each other’s effect on GI motility

Question 7

Sodium bicarbonate is ______ acting but not useful for ______

Answer 7

Fast acting

Ulcer

Question 8

Burps following use of sodium bicarbonate are due to …

Answer 8

CO2

Question 9

If sodium bicarbonate is absorbed, it can cause…

Answer 9

Metabolic alkalosis

Question 10

Sodium bicarb should be used with caution in …

Answer 10

CHF

Duh, it’s got sodium in it you fool

Question 11

What are tums really?

Answer 11

Calcium carbonate

Question 12

What can happen if you take too many tums?

Answer 12

“Milk alkali” syndrome

Can also have acid rebound because Ca2+ stimulates acid production

Question 13

Magnesium hydroxide is used as a _______

Answer 13

Laxative

Because it causes diarrhea

Poorly absorbed but may accumulate if renal function poor

Question 14

How is aluminum hydroxide used?

Answer 14

Causes constipation so is combined with magnesium to cancel each other out

May accumulate if decreased renal function

Question 15

How are antacids used?

Answer 15

Temporary relief of heartburn, gastritis

Adjunct to other drugs, b/c effect is quick

Systemic effects rare - but renal function is important

Watch Na2+ in patients with CHF

Remember drug interactions!

Question 16

What is the main reason for drug interactions with antacids?

Answer 16

They affect absorption of drugs or form insoluble complexes with them

Form complexes with THEOPHYLLINE, KETOCONAZOLE, QUINOLONE ABX, TETRACYCLINE

Decrease absorption of DIGOXIN, PHENYTOIN, PROPRANOLOL

Increase elimination of PHENOBARBITAL, SALICYLATES (B/C THEY ALKALINIZE URINE)

Question 17

MOA for H2 antagonists

Answer 17

Decrease GI acid formation through H2 receptor blockade

Question 18

What are the H2 antagonists?

Answer 18

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

All are OTC

Question 19

Why is Cimetidine special?

Answer 19

B/c it inhibits metabolism and also has an antiandrogen effect

Question 20

How are H2 blockers used?

Answer 20

To treat and prevent ulcers

As adjuncts in GERD

Pre-anesthesia

With H1 blockers for severe allergic reaction

Question 21

When are H2 blockers most effective?

Answer 21

When taken at night

Question 22

What side effects do you get with H2 blockers?

Answer 22

Few, but they are worse in the elderly

Headache, dizziness, nausea

Rash, itchiness

Question 23

Side effects of Cimetidine specifically

Answer 23

Some anti-testosterone effect - may be useful in women

Chronic, high doses may cause gynecomastia, loss of libido, and impotence in men

Inhibits metabolism of many drugs by CYP3A4 (warfarin, phenytoin, theophylline, digoxin)

Question 24

The “prazoles” are all _______

Answer 24

Proton pump inhibitors

Question 25

MOA for proton pump inhibitors

Answer 25

Irreversibly block acid formation by the gastric parietal cells

New pumps will form so duration of action is about 2-3 days

Question 26

Drugs of choice for GERD

Answer 26

Proton pump inhibitors

Question 27

Which drugs are proton pump inhibitors?

Answer 27

The “prazoles”

Omeprazole
Esomeprazole
Lansoprazole
Rabeprazole
Pantoprazole

Question 28

Proton pump inhibitors are administered as _______ and activated in ______

Answer 28

Pro-drugs

Parietal cells to sulfenamide

Question 29

How long do PPIs last?

Answer 29

Long-lasting: 24-48 hours to start to replace the irreversibly blocked pumps

Can be given QD but take 2-5 days for max effect

Question 30

How should you take PPIs?

Answer 30

Best to take on an empty stomach and eat 30 min later

Given QD but take 2-5 days for max effect

Question 31

Why do PPIs have very few side effects?

Answer 31

B/c they are pro drugs and only converted to active form in the parietal cells themselves

Question 32

Side effects of PPIs

Answer 32

Nausea, diarrhea, colic

OSTEOPOROSIS - b/c decreased Ca@+ absorption

Decreased Mg2+ absorption

HA, dizziness, sleepiness uncommon

Increased ALT, AST (rare)

OMEPRAZOLE MAY INHIBIT CYP2C19 (phenytoin, warfarin, diazepam, Clopidigrel)

Decreased B12 absorption

Increased chance of PNA****

Question 33

When are PPIs indicated?

Answer 33

Ulcers that haven’t responded to H2 antagonists (duodenal ulcer >4 weeks or gastric ulcer >8 weeks)

DOC for GERD**

Patients on NSAIDs

Zollinger-Ellison Syndrome

Question 34

Old med for PUD that works as a prostaglandin E1 analogue

Answer 34

Misoprostol (Cytotec)

Question 35

MOA for misoprostol (Cytotec)

Answer 35

Prostaglandin E1 analogue

Question 36

How is Misoprostol (Cytotec) used/

Answer 36

To prevent or reduce NSAID-induced damage

Diarrhea, nausea, HA, dizziness can occur

DO NOT USE IN PREGNANCY - can induce an abortion