GI Flashcards
Antihistamines
Cimetidine, Ranitidine, Famotidine, Nizatidine
MOA:
Reversible block of histamine H2 receptors –> dec. H+ secretion by parietal cells
Use:
Peptic ulcer
Gastritis
Mild esophageal reflux
Adv. effects (CImetidine):
CYP P450 inhibitor
Antiandrogenic effects (prolactin release, gynecomastia, impotence,dec. libido in males)
Can cross BBB (confusion, dizziness, headaches)
Can cross placenta
Adv. effects (Cimetidine, Ranitidine):
Decrease renal excretion of creatinine
Proton pump inhibitors
Omeprazole, Lansoprazole, Esomeprazole, Pantoprazole, Dexlansoprazole
MOA:
Irreversibly inhibit H+/K+ ATPase in stomach parietal cells
Use: Peptic ulcer Gastritis Esophageal reflux Zollinger-Ellison syndrome
Adv. Effects:
Increased risk of C. difficile infection
Pneumonia
Decrease serum Mg2+ with long term use
Antacids
Affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and urniary pH or by delaying gastric emptying
All can cause hypokalemia
Overuse:
Aluminum hydroxide - Constipation, hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures
Calcium carbonate - Hypercalcemia (milk-alkali syndrome), rebound acid increased; can chelate and decrease effectiveness of other drugs (ex, tetracycline)
Magnesium hydroxide - Diarrhea, hyporeflexia, hypotension, cardiac arrest.
Bismuth, sucralfate
MOA:
Bind to ulcer base, providing physical protection and allowing HCO3 secretion to reestablish pH gradient in the mucous layer
Use:
Increase ulcer healing, traveler’s diarrhea
Misoprostol
MOA:
PGE1 analog
Increase production and secretion of gastric mucous barrier
Decrease acid production
Use:
Prevention of NSAID-induced peptic ulcers (NSAIDs block PGE1 production)
Maintenance of a PDA
Off-label for induction of labor (ripens cervix)
Adv. effects:
Diarrhea
Contraindicated in women of childbearing potential
Octreotide
MOA:
Long acting somatostatin analog
Inhibits secretion of various splanchnic vasodilatory hormones
Use: Acute variceal bleeds Acromegaly VIPoma Carcinoid tumors
Adv. effects: Nausea Cramps Steatorrhea Increase risk of cholelithiasis due to CCK inhibition
Osmotic laxatives
Magnesium hydroxide, Magnesium citrate, Polyethylene glycol, Lactulose
MOA:
Provide osmotic load to draw water into the GI lumen
Use:
Constipation
Lactulose treats hepatic encephalopathy (bc gut flora degrades it into metabolites that promote nitrogen excretion)
Adv. effects:
Diarrhea
Dehydration
May be abused by bulimics
Sulfasalazine
MOA:
Combination of sulfapyridine (antibacterial) and 5-aminosalicyclic acid (anti-inflammatory)
Activated by colonic bacteria
Use:
Ulcerative colitis
Crohn disease
Adv. effects: Malaise Nausea Sulfonamide toxicity Reversible Oligospermia
Loperamide
MOA:
Agonist at u-opioid receptors
Slow gut motility
Poor CNS penetration (low addictive potential)
Use:
Diarrhea
Adv. effects:
Constipation
Nausea
Ondansetron
MOA:
5-HT3 antagonist
Decrease vagal stimulation
Powerful central-acting antiemetic
Use:
Control vomiting postoperatively and in patients undergoing cancer chemotherapy
Adv. effects:
Headache, Constipation, QT interval prolongation
Metoclopramide
MOA:
D2 receptor antagonist
Increase resting tone, contractility, LES tone, motility
Does not influence colon transport time
Use:
Diabetic / postsurgery gastroparesis
antiemetic
Adv. effects:
Increased parkinsonian effects, tardive dyskinesia
Restlessness, drowsiness, fatigue, depression, diarrhea
Drug interaction with digoxin and diabetic agents.
Contraindicated in patients w/ small bowel obstruction or Parkinson disease (due to D2 receptor blockade)
Orlistat
MOA:
Inhibits gastric and pancreatic lipase –> decrease breakdown and absorption of dietary fats
Use:
Weight loss
Adv. effects:
Steatorrhea
Decrease absorption of fat-soluble vitamins
Ursodiol
MOA:
Nontoxic bile acid
Increase bile secretion
Decrease cholesterol secretion & reabsorption
Use:
Primary biliary cirrhosis
Gallstone prevention or dissolution
