Wk2 Acid/Peptic disease drugs Flashcards
Metronidazole inhibits which enzyme causing drug interactions?
CYP2C9
Major drug interactions due to metronidazole’s inhibition of CYP2C9:
potentiates warfarin
Cimetidine’s effect on metronidazole?
decreases clearance –> potentiates effects
bacterioCIDAL
cell wall inhibitor (beta-lactam)
hypersensitivity
amoxicillin
Why clarithromycin vs azithromycin for H. pylori?
MIC90 of .06 vs .25
more acid stable
bacterioSTATIC
protein synthesis inhibitor (binds to 50s ribosomal RNA to prevent translocation)
GI irritation, drug interactions (both a substrate and an inhibitor of CYP3A4)
clarithromycin
Two ways antimuscarinics decrease H+ secretion:
- Block M3 receptors on ECL cells preventing their release of histamine (–> parietal cell stimulation)
- directly block M3’s on parietal cells
IRREVERSIBLY block the final common pathway in acid secretion — H+/K+ ATPase.
PPIs
“-Prazoles”
**make sure there is a P
sulfate-aluminum hydroxide complex that attaches to the basement membrane of the ulcer
constipation
requires acidic environment to become paste
sucralfate
direct (but limited) antimicrobial activity against H. pylori
disrupts cell wall, causing lysis
prevents adhesion
inhibits urease
protects ulcer surface
coats ulcer surface, protecting it from acid and pepsin
stimulates prostaglandin, mucous and bicarbonate secretion
Bismuth
blackening of stool and tongue
Bismuth
(PGE1) drug of choice for treatment of ulcers induced by NSAIDs
side effects and the need for frequent dosing limit its use.
It is abortifacient. CONTRAINDICATED in pregnancy.
misoprostol
Abx that get chelated and is less effective when taken with antacids:
tetracycline
highly selective, competitive inhibitor of parietal cell H2 receptors
reduce intracellular cAMP
cimetidine
FAMOTIDINE, NIZATIDINE, RANITIDINE, ROXATIDINE
Two antimuscarinics:
atropine
pirenzipine
**no longer used due to big side fx
Time for PPIs to take full effect:
3-4 days
Fart blocker
simethicone
rapid onset but short duration of action
no prevention of ulcer recurrence
useful for intermittent dyspepsia
antacids
relatively rapid onset
intermediate duration, some prevention
many uses
H2 blockers
slow onset of action
very long duration of action
excellent prevention
drugs of choice for Zollinger-Ellison syndrome and GERD, as well as ulcer treatment
PPIs
excessive consumption of high calcium foods with certain antacids, over a long period of time
milk-alkali syndrome
Antacid
efficient
low systemic absorption
constipation
not very effective when given alone
osteomalacia (RARE)
Aluminum hydroxide
Antacid
efficient
low systemic absorption
osmotic diarrhea
(RARE) renal insufficiency → hypermagnesemia → CNS & cardio-toxicity
Magnesium hydroxide
Antacid
rapid onset of action
long duration
belching, gastric distension
rebound acid secretion
(RARE) mild systemic alkalosis
(RARE) hypercalcemia in patients with impaired renal function if taken with dairy products (milk-alkali syndrome)
Calcium carbonate
