Flashcards in G.I. Drugs Deck (88)
Two major classes of drugs affecting the GI system
Drugs affecting secretion
Drugs affecting GI motility
Classes of drugs affecting secretion
H2 histamine receptor antagonists
Proton pump inhibitors
Class of drugs affecting GI motility
Drugs affecting GI secretions are used in the treatment of
1. Peptic ulcers (gastric or guodenal)
2. Gastroesophageal reflux (GERD/Barrett's Esophagus)
3. Hypersecretory states such as Zollinger-Ellison syndrome
Ulcers are a failure of
What do proton pump inhibitors inhibit
H+/K+ ATPase in the parietal cells
Name the 4 antacids
Adverse effects of NaHCO3
systemic alkalosis, fluid retention
Adverse effects of CaCO3
Milk-alkali syndrome: hypercalcemia and nephrolithiasis
Adverse effects of Al(OH)3
Constipation and hypophosphatemia
Adverse effects of Mg(OH)2
Diarrhea and hypermagesemia
What is Alternagel?
What is Mallox and Mylanta?
Al(OH)3 and Mg(OH)2
What is Tums?
What is Gaviscon and what does it do?
Sodium alginate + antacids: viscous, weak base; prevents reflex and effective in GERD
What is Mylicon/Phazyme and what do they do?
Simethicone: mild surfactant; enhances the release of gas
First generation H2-histamine receptor antagonists
Diphenhydramine and Cimetidine
Mechanism of Cimetidine
competitive antagonist of H2 histamine receptor
Cimetidine reduces gastric acid secretion in response to what?
in response to histamine, gastrin, and acetylcholine
Cimetidine inhibits which metabolic enzymes? Which drugs does this effect?
Inhibits CYP 2C6 and 2D9: warfarin, phenytoin, theophylline, benzodiazepines and sulfonylureas
Side effects of Cimetidine?
1. CNS effects (confusion, delirium headaches) seen with IV admin to elderly patients
2. Antiandrogen (gynecomastia, impotence)
3. Inhibition of estradiol metabolism (galactorrhea)
Second generation H2 blockers
Ranitidine (Zantac); Nizatidine (Axid); Famotidine (Pepcid)
How are second generation H2 blockers different from 1st generation H2 blockers?
longer half life; increase ethanol bioavailability by reducing first-pass metabolism (except Famotidine); fewer effects of CYP450 system; greater potency
Proton pump inhibitors (PPIs)
Omeprezole; lansoprazole; raberprazole, pantoprazole
Action of proton pump inhibitors
Irreversible inhibitor of H+/K+ ATPase
What are PPIs activated by?
Prodrugs: activated by acidic pH
Describe the pharmacokinetics of PPIs
Short plasma half-life (~1hr) but long duration of action (>24 hrs)
PPIs can cause hypergastrinemia, which can result in?
can result in rebound hypersecretion of gastric acids
Increase in gastric pH with PPIs can affect what?
drug absorption and potentially increase risk of infections