2 GI Drugs Flashcards
How do Peptic Ulcers form?
Mucous and bicarb normally protect stomach lining, but increased acid overcomes protective mechanisms
Increased acid can be due to:
Stress
NSAIDs
H. pylori infection
What are the different approaches to treating peptic ulcers?
Decrease stomach acid
Eliminate H. pylori
Protect mucosa
What four drugs do you use in combo to treat H. pylori infection?
Pepto-Bismol
Metronidazole
Clarithromycin, tetracycline, or amoxicillin
H2 blocker
What are Antacids exactly?
Inorganic bases, often divalent cations
Neutralize acid by directly binding to HCl
Can be aluminum, magnesium, calcium, or sodium bicarb
Which antacid causes diarrhea?
Magnesium
Which antacid causes constipation?
Aluminum
Aluminum and magnesium often combined to cancel each other’s effect on GI motility
Sodium bicarbonate is ______ acting but not useful for ______
Fast acting
Ulcer
Burps following use of sodium bicarbonate are due to …
CO2
If sodium bicarbonate is absorbed, it can cause…
Metabolic alkalosis
Sodium bicarb should be used with caution in …
CHF
Duh, it’s got sodium in it you fool
What are tums really?
Calcium carbonate
What can happen if you take too many tums?
“Milk alkali” syndrome
Can also have acid rebound because Ca2+ stimulates acid production
Magnesium hydroxide is used as a _______
Laxative
Because it causes diarrhea
Poorly absorbed but may accumulate if renal function poor
How is aluminum hydroxide used?
Causes constipation so is combined with magnesium to cancel each other out
May accumulate if decreased renal function
How are antacids used?
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!
What is the main reason for drug interactions with antacids?
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)
MOA for H2 antagonists
Decrease GI acid formation through H2 receptor blockade
What are the H2 antagonists?
Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pepcid)
Nizatidine (Axid)
All are OTC
Why is Cimetidine special?
B/c it inhibits metabolism and also has an antiandrogen effect
How are H2 blockers used?
To treat and prevent ulcers
As adjuncts in GERD
Pre-anesthesia
With H1 blockers for severe allergic reaction
When are H2 blockers most effective?
When taken at night
What side effects do you get with H2 blockers?
Few, but they are worse in the elderly
Headache, dizziness, nausea
Rash, itchiness
Side effects of Cimetidine specifically
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)
The “prazoles” are all _______
Proton pump inhibitors
