GI pharm Flashcards
H2 blockers include cimetidine, ranitidine, famotidine, nizatidine. What’s the mech of action? Clinical use? Toxicity?
mech: reversible block of histamine H2-receptors to decrease H+ secretion by parietal cells.
clinical use: peptic ulcer, gastritis, mild esophageal reflux
toxicity: potent inhibitor of CYP450 (multiple drug interactions); anti-androgenic effects (prolactin release, gynecomastia, impotence, decrease libido in males); can cross BBB (confusion, dizziness, headaches), and placenta.
* both cimetidine and ranitidine decrease renal excretion of creatinine
Which 2 H2 blockers decrease renal excretion of creatinine?
cimetidine
ranitidine
The proton pump inhibitors (omeprazole, lansoprazole, esomeprazole, pantoprazole, dexlansoprazole) irreversibly inhibit H+/K+ ATPase in stomach parietal cells. What 4 conditions are they used to treat?
- peptic ulcer
- gastritis
- esophageal reflux
- ZES
Of all the proton pump inhibitors, which one is the least likely to to have drug-drug interactions?
pantoprazole
What are 3 side effects assoc with H+ pump inhibitor usage?
- increased risk of C. diff infection
- pneumonia
- decrease serum Mg2+ with long-term use.
What are bismuth and sucralfate used in? Mech of action?
Sucralfate and bismuth bind to ulcer base, providing physical protection and allowing HCO3- secretion to establish pH gradient in the mucuous layer.
clinical use: increase ulcer healing, traveler’s diarrhea
What is misoprostol? What are some of its clinical uses? Toxicity?
Misoprostol is a PDE1 analog that increases production and secretion of gastric mucous barrier, and decreases acid production.
Prevention of NSAID-induced peptic ulcers (NSAIDs block PGE1 production); maintenance of a PDA. Also, used off-label for induction of labor (ripens cervix).
Toxicity: Diarrhea, contraindicated in women of childbearing potential b/c it’s an abortifacent
What is Octreotide? What is it used in? Toxicity?
Octreotide is a long-acting somastatin analog; inhibits actions of many splanchnic vasoconstriction hormones used in acute variceal bleeds, acromegaly, VIPoma, carcinoid tumors.
toxicity: nausea, cramps, steatorrhea
Antacids can affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and urinary pH or by delaying gastric emptying. List the 3. All can cause HYPOKALEMIA and their specific side effects.
All can cause hypokalemia
- aluminum hydroxide: constipation and hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures
- calcium carbonate: hypercalcemia, rebound acidity
- magnesium hydroxide: diarrhea, hyporeflexia, hypotension, cardiac arrest
Osmotic laxatives include magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose. They provide osmotic load to draw water into the GI lumen. What are some clinical uses and toxicity?
- constipation
- lactulose treats hepatic encephalopathy since gut flora degrade it into metabolites (lactic acid + acetic acid) that acidify the lumen and promote nitrogen excretion as NH4+
toxicity: diarrhea, dehydration, may be abused by bulimics
T/F: bulimics may abuse osmotic laxatives like magnesium citrate, magesium hydroxide, polyethylene gylcol and lactulose.
True
What is sulfasalazine? Clinical use and toxicity?
Sulfasalazine = sulfapyridine (antibacterial) + 5-aminosalicyclic acid (anti-inflammatory); activated by colonic bacteria
Uses: ulcerative colitis, crohn disease
toxicity: malaise, nausea, sulfonamide toxicity, reversible OLIGOSPERMIA
What is ondansetron’s mech of action? Clinical use? toxicity?
Ondansetron is a 5-HT3 antagonist that decreases vagal stimulation. It is a powerful central-acting anti-emetic
Uses: control vomiting post-op and in patients undergoing cancer chemo
Toxicity: headache, constipation, QT interval prolongation (risk of torsades)
What is metoclopramide? Uses? Toxicities?
Metoclopramide is a D2 receptor antagonist that increases resting tone, contractility, LES tone, motility. DOES NOT influence colon transport time.
Uses: diabetic and postsurgery gastroparesis, antiemetic
Toxicity: increase parkinsonian effects, tardive dyskinesia, restlessness, drowsiness, fatigue, depression, diarrhea.
What are some drug interactions that you need to be wary of with metoclopramide?
What 2 conditions is metoclopramide contraindicated in?
- drug interactions with digoxin and diabetic agents
* Contraindicated in pts with small bowel obstruction or Parkinson disease (D1-receptor blockade)
