GI drugs Flashcards
What is the mechanism of ranitidine/cimetidine/famotidine/nizatidine?
Reversible block of histamine H2 receptors : Decrease H+ secretion by parietal cells.
What are the clinical uses of ranitidine/cimetidine/famotidine/nizatidine?
Peptic ulcer, gastritis, mild esophageal reflux.
What are the side effects of cimetidine?
- Potent C-P450 inhibitor
- Anti-androgenic effects (prl, gynecomastia, impotence, decr libido)
- BBB crosser (confusion, dizziness, etc)
- Crosses placenta
- Decr renal excretion of creatinine
Which other H2 blocker decreases renal excretion of Cr?
Ranitidine
What is the mechanism of action of Omeprazole, lansoprazole, esomeprazole, pantoprazole, dexlansoprazole.
Irreversibly inhibit H+/K+ ATPase in stomach parietal cells.
What is the clinical use of proton pump inhibitors?
Peptic ulcer, gastritis, esophageal reflux, Zollinger-Ellison syndrome.
What are the side effects of PPIs?
Increased risk of C. diff infection, pneumonia, decr serum Mg2+ with long term use
What is the mechanism of action of bismuth and sucralfate?
Bind to ulcer base, providing physical protection and allowing HCO3– secretion to reestablish pH gradient in the mucous layer.
What is the clinical use for bismuth and sucralfate?
Incr ulcer healing, travelers’ diarrhea.
What is the mechanism of misoprostol?
A PGE1 analog. Increases production and secretion of gastric mucus barrier, decreases acid production. Ripens cervix as well.
What is the clinical use of misoprostol?
- Prevention of NSAID-induced peptic ulcers (NSAIDs block PGE1
production) - Maintenance of a
PDA. - Also used off-label for induction of labor (ripens cervix).
What is the mechanism of action of octreotide?
Long-acting somatostatin analog; inhibits actions of many splanchnic vasoconstriction hormones.
What are the clinical uses of octreotide?
Acute variceal bleeds, acromegaly, VIPoma, carcinoid tumors.
What are the toxicities associated with octreotide?
Nausea/cramps/steatorrhea
Why do antacids interfere with other drugs?
Can affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and
urinary pH or by delaying gastric emptying.
What electrolyte abnormality is associated with antacids?
hypokalemia
Antacid overuse of aluminum hydroxide can cause?
Constipation and hypophosphatemia; proximal
muscle weakness, osteodystrophy, seizures
Antacid overuse of calcium carbonate can cause?
Hypercalcemia, rebound acid increase; chelation of other drugs such as tetracycline
Antacid overuse of magnesium hydroxide accumulation can cause?
Diarrhea, hyporeflexia, hypotension, cardiac
arrest
What drug class are Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose?
Osmotic laxatives
What is the mechanism of action of Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose?
Provide osmotic load to draw water into the GI lumen.
What is the clinical use for osmotic laxatives?
Constipation
What is lactulose also used for? How does it work?
Lactulose also treats hepatic encephalopathy since gut flora degrade it into metabolites (lactic acid and acetic acid) that promote nitrogen excretion as NH4+.
What toxicity is associated with osmotic laxatives?
Diarrhea, dehydration; may be abused by bulimics.
What is the mechanism of action of sulfasalazine?
A combination of sulfapyridine (antibacterial) and 5-aminosalicylic acid (anti-inflammatory).
Activated by COLONIC bacteria.
What is the clinical use of sulfasalazine?
Ulcerative colitis, Crohn disease (colitis component).
What toxicities are associated with sulfasalazine?
Malaise, nausea, sulfonamide toxicity, reversible oligospermia
What is the mechanism of action of odansetron?
5-HT3 antagonist; decr vagal stimulation. Powerful
central-acting antiemetic.
What is the clinical use for odansetron?
Control vomiting postoperatively and in patients
undergoing cancer chemotherapy.
What are the toxicities associated with odansetron?
Headache, constipation, QT interval
prolongation.
What is the mechanism of action of metoclopramide?
D2 receptor antagonist. Increases resting tone, contractility, LES tone, motility. Does not influence colon transport time.
What is the clinical use for metoclopramide?
Diabetic and postsurgery gastroparesis, antiemetic.
What is the toxicity associated with metoclompramide?
- Parkinsonian effects, TD etc
2. Drug interaction with digoxin and diabetic agents
What are the contraindications for metoclopramide?
In patients with small bowel obstruction of parkinson’s disease
What is the mechanism of orlistat?
Inhibits gastric and pancreatic lipase, decreases breakdown and absorption of dietary fats.
What is the clinical use for orlistat?
Weight loss
What are the side effects of orlistat?
Steatorrhea, decr absorption of fat soluble vitamins
