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11 terms

Pharm - Gastrointestinal

First Aid 2012 pg 368-370 Drug vs Mechanism/Clinical use/toxicity, when applicable.
H2 blockers (Cimetidine, Ranitidine, Famotidine, Nizatidine, Loratidine)
Mech: Reversible block of histamine H2 receptors --> decreased H+ secretion by parietal cells
Use: Peptic ulcer, gastritis, mild esophageal reflux
Tox: Cimetidine is a potent inhibitor of P450; it also has anti-andorgenic effects (prolactin release, gynecomastia, impotence, decreased libido in males); can cross BBB (confusion, dizziness, headaches) and placenta. Both cimetidine nad ranitidine decrease renal excretion of creatinine. Other H2 blockers are relatively free of these effects.
Proton Pump Inhibitors (Omeprazole, Lansoprazole)
Mech: Irreversibly inhibit H/K/ATPase in stomach parietal cells.
Use: Peptic ulcer, gastritis, esophageal reflux, Zollinger-Ellison syndrome
Bismuth, Sucralfate
Mech: Bind to ulcer base, providing physical protection, and allow HCO3- secretion to reestablish pH gradient in mucous layer.
Use: Increase ulcer healing, traveler's diarrhea
Mech: A PGE1 analogue. Increase prodcution and secretion of gastric mucous barrier, decrease acid production.
Use: Prevention of NSAID-induced peptic ulcers; maintenance of a PDA. Also used to induce labor.
Tox: Diarrhea. Contraindicated in women of childbearin potential (aboritfactient)
Mech: Long-acting somatostatin analogue
Use: Acute variceal bleeds, acromegaly, VIPoma, carcinoid tumors
Tox: Nausea, cramps, steatorrhea
Antacids (Aluminum hydroxide, Magnesium hydroxide, Calcium carbonate)
NOTE: Affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and urinary pH or by delaying gastric emptying.
Tox: Aluminum hydroxide: constipation and hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures.
Magnesium hydroxide: diarrhea, hyporeflexia, hypotension, cardiac arrest.
Calcium carbonate: hypercalcemia, rebound acid increases.
All can cause hypokalemia.
Osmotic Laxatives (Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose)
Mech: Provide osmotic load to draw water out.
Use: Constipation. Lactulose also treats hepatic encephalopathy since gut flora degrade it into metabolites (lactic and acetic acid) that promote nitrogen excretion as NH4+
Tox: Diarrhea, dehydration; may be abused by bulimics
Mech: Monoclonal Ab to TNF
Use: Crohn's disease, rheumatoid arthritis
Tox: Infection (including reactivation of latent Tb), fever, hypotension
Mech: A combination of sulfapyridine (antibacterial) and 5-aminosalicylic acid (anti-inflammatory). Activated by colonic bacteria.
Use: Ulcerative colitis, Crohn's disease
Tox: Malaise, nausea, sulfonamide toxicity, reversible oligospermia
Mech: 5-HT3 antagonist. Powerful central acting antiemetic.
Use: Control vomiting post-operatively and in patients undergoing cancer chemotherapy
Tox: Headache, constipation
Mech: D2 receptor antagonist. Increases resting tone, contractility, LES tone, motility. Does not influence colon transport time.
Use: Diabetic and post-surgery gastroparesis
Tox: Increase parkinsonian effects. Restlessness, drowsiness, fatigue, depression, nausea, diarrhea. Drug interaction with digoxin and diabetic agents. Contraindicated in patients with small bowel obstruction or Parkinson's disease.