GI drugs Flashcards
Antibiotics given to fight H. pylori
Amoxicillin-preferre
Carithromycin- increasing resistance
Metronidazole-alternative for allergy
Tetracycline-for quadruple therapy
MOA of bismuth subsalicylate
antibacterial activity against H. pylori
binds E. coli enterotoxins
forms a barrier
anti-secretory and anti-inflammatory activities of salicylate
Therapeutic use of bismuth subsalicylate
PUD, diarrhea, nausea and cramping
Adverse effects of bismuth subsalicylate
harmless black discoloration of stool and tongue, salicylism at high doses (tinnitus) Reye’s syndrome, use with caution in children
Antacid prototypes
magnesium hydroxide and aluminum hydroxide
MOA of antacids
raise stomach pH
Pharmacokinetics of antacids
1-2 hrs
Differences between Mg and Al hydroxide
Mg2+ -diarrhea due to peristaltic stimulation, Al smooth muscle relaxation
Therapeutic use of antacids
largely replaced by more effective, mild symptoms
Drug interactions of antacids
can interfere with absorption of other drugs
Prototype histamine receptor antagonists
cimetidine
MOA of histamine receptor antagonists
blocks acid secretion from parietal cells stimulated by histamine, highly selective for H2
Therapeutic use of H2R antagonists
supress total acid secretion by 70%, most effective in suppressing nocturnal acid secretion
Slower onset and longer duration than antacids, prophylactic
Tolerance can develop
Adverse reactions of H2R antagonists
edocrine effects- loss of libido, impotence and gynocomastia
CNS effects- rare, in elderly with decreased liver/kidney function
Pneumonia-increased bacterial colonization
Drug interactions with H2R antagonists
cimetidine inhibits multiple cyp isoforms
Prototype PPI
omeprazole
MOA of PPIs
irreversibly inhibits H+, K+ ATPase that are active
Pharmacokinetics of PPI
30 min before meals, reduces acid secretion by 95%, effects persist for 2-3 days
Enteric coated to get to small intestine
Metabolism of PPIs
hepatic metabolism by CYPs, asian variant correlates with slow metabolism, dose reduction in patients with hepatic disease
Therapeutic uses of PPI
PUD, GERD, Zollinger-Ellison syndrome, NSAIDs associated ulcers
Adverse reactions of PPIs
nausea, abdominal pain, constipation/diarrhea, flatulence
pneumonia
fractures due to decreased Ca+ absorption
rebound hypersecretion upon discontinuation
Drug interactions with PPIs
warfarin, diazepam, cyclosporine
Mucosal protective agent prototype
sucralfate
MOA of sucralfate
forms a gel at low pH, binds necrotic tissue forming a barrier to acid and pepsin
Therapeutic use of sucralfate
duodenal and stress ulcers, stomach pH not increased, does not increase pneumonia risk
Adverse reactions of sucralfate
constipation, reduced absorption of other drugs