GI Drugs Flashcards
H2 blockers
Cimetidine, Ranitidine, Famotidine, Nizatidine
*Take before you DINE, Table for 2”
Mechanism of H2 blockers
reversibly block histamine (H2) receptors on parietal cell
decreases H+ secretion by parietal cells
Clinical use of H2 blockers
peptic ulcer
gastritis
mild GERD
toxicity of H2 blockers
Most H2 blockers are relatively free of S/E
Ranitidine– decreases renal excretion of creatinine
Cimetidine–
potent inhibitor of p450 = multiple drug interactions
antiandrogenic effects (inc PRL release = gynecomastia, impotence & dec libido in males)
can cross BBB (confusion, dizzy, HA) & placenta
decreases renal excretion of creatinine
Proton Pump Inhibitors
Omeprazole lansoprazole pantoprazaole esomeprazole dexlansoprazole
(-prazole)
Mechanism of PPI’s
irreversibly inhibit H/K ATPase in stomach parietal cells
Clinical use of PPIs
Peptic Ulcer
Gastritis
GERD
Zollinger-Ellison syndrome
toxicity of PPIs
inc risk of C. diff infxn & pneumonia
Hip fx
dec serum Mg with long-term use
Bismuth & Sucralfate MOA
bind to ulcer base = physical protection
allows HCO3 secretion to re-establish pH gradient in the mucus layer
clinical use of bismuth & sucralfate
traveler’s diarrhea
ulcer healing
Misoprostol MOA
PGE1 analog (prostaglandin)
increases production & secretion of gastric mucous barrier
decreases acid production
clinical use of Misoprostol
prevents NSAID-induced peptic ulcers maintains PDA induces labor (ripens cervix)
Toxicity of Misoprostol
Diarrhea
CONTRA if childbearing potential (abortifacient)
Octreotide MOA
long-acting somatostatin analog (inhibits GF)
Clinical use of Octreotide
Acute variceal bleeds
VIPoma
carcinoid tumor
(and tx acromegaly)
toxicity of Octreotide
nausea, cramps, steatorrhea
Antacid types
Aluminum Hydroxide
Magnesium Hydroxide
Calcium Carbonate
MOA & S/E of all antacids
affects absorption, bioavailability or urinary excretion of other drugs by altering gastric & urinary pH, or by delaying gastric emptying.
causes hypokalemia
Aluminum hydroxide S/E
constipation (MINIMUM feces) hypophosphatemia proximal muscle weakness osteodystrophy seizures
Magnesium hydroxide S/E
Diarrhea (Must Go)
hyporeflexia
hypotension
cardiac arrest
Calcium carbonate S/E
hypercalcemia
rebound acid increase
decreases other drug effectiveness (chelates)– esp tetracycline
Osmotic Laxatives
magnesium hydroxide
magnesium citrate
polyethylene glycol
lactulose
MOA of osmotic laxatives
provide osmotic load = draws water out into lumen
lactulose also treats hepatic encephalopathy– since gut flora degrade it into metabolites of lactic acid & acetic acids (promote nitrogen excretion as NH4+)
clinical use of osmotic laxatives
constipation
toxicity of osmotic laxatives
diarrhea
dehydration
*abused by bulimics
Infliximab MOA
monoclonal antibody to TNF-alpha
-mab = monoclonal Ab
use of Infliximab
Crohn’s Dz
Ulcerative colitis
Rheumatoid arthritis
Toxicity of Infliximab
infection (reactivation of latent TB)
fever
hypotension
Sulfasalazine MOA
combo of sulfapyridine (antibacterial) & 5-aminosalicylic acid (anti-inflammatory)
activated by colonic bacteria
Use of Sulfasalazine
Ulcerative Colitis
Crohn’s
Toxicity of Sulfasalazine
Malaise
Nausea
reversible oligospermia
sulfonamide toxicity
Ondansetron MOA
5-HT3 antagonist
powerful centrally-active antiemetic
Clinical Use of Ondansetron
control vomiting postop
chemotherapy pts
S/E of Ondansetron
HA, constipation
Metoclopramide MOA
D2 receptor antagonist
increases resting tone, contractility, LES tone, motility.
does NOT influence colon transport time
Clinical use of Metaclopramide
Diabetic
Post-surgery gastroparesis
Antiemetic
Toxicity of Metaclopramide
Inc parkinsonian effects
restlessness, drowsiness, fatigue, depression, nausea, diarrhea
*drug interaction w/ digoxin & diabetic tx
*CONTRA in pts with small bowel obstruction & parkinson’s disease
What is octreotide used for?
Esophageal varices
How does octreotide work in treating esophageal varices?
Decreases glucagon and VIP which vasodilate splanchnic vessels.
Causes vasoconstriction of splanchnic vessels thereby diverting blood flow to the systemic circulation.
Does not cause systemic circulation vasoconstriction
What is pentagastrin?
A gastrin analog used to screen for carcinoid syndrome and medullary carcinoma of the thyroid
What over the counter drug may reduce the risk of adenomatous polyp formation in the colon?
aspirin - some colon adenomas have shown over expression of COX2
What is diphenoxylate?
An opiate anti-diarrheal structurally related to meperidine.
What is the MOA of diphenoxylate?
Binds mu receptors in the GI tract and causes slower motility.
What are the side effects of diphenoxylate?
Bloating and mild sedation
Can cause euphoria and physical dependence
What is diphenoxylate combined with to prevent abuse?
Atropine - causes dry mouth, blurry vision and nausea at higher doses.
Atropine + diphenoxylate = lomotil
What are the drugs that target secretory diarrhea?
Bismuth salicylate
Probiotics
Octreotide
