Upper GI Pharmacology Flashcards
Antacid pharmacokinetics
tablets/powder, suspension Poorly absorbed (unless poor renal function), thus minimal undesired systemic side effects Di/tri-valent cations; may chelate other drugs, separate dosing
Antacid MOA
Locally buffer H+ to increase pH
Antacid indications
heartburn, dyspepsia
Antacid SE
Mg-containing: osmotic diarrhea (explosive)
Ca-containing: constipation, hypercalcemia, calculi, bloating, nausea (due to CO2 liberated)
Al-containing: constipation, hyperphosphatemia
H2 antagonist prototypes
ranitidine, cimetidine
H2 antagonist PK
po; some iv and im
rapidly absorbed
renal elimination (filtration and secretion) - adjust dosing in renally impaired patients
Cimetidine: notorious CYP450 blocker
H2 antagonist MOA
H2 receptors on parietal cells mediate basal, nocturnal, and meal-stimulated release of acid (histamine binding stimulates H/K ATPase via cAMP)
Reversible blockage
H2 antagonist indications
GERD
PUD
Dyspepsia
Prevention of bleeding from stress-related gastritis
H2 antagonist SE
generally well-tolerated
diarrhea/constipation, headache, fatigue, MSK pain
Cimetidine only: gynecomastia and galactorrhea
PPI prototypes
omeprazole, pantoprazole
PPI PK
must be absorbed into systemic circulation
act locally on GI tract cells (parietal cells)
Prodrugs: activated in acidic canaliculi of parietal cells
hepatic clearance - adjust dosing in liver impaired patients
PPI MOA
antagonist of proton-secreting pump in stomach (K/H pump) on parietal cells
irreversible
PPI indications
gastric and duodenal ulcers, NSAID-induced ulcers
GERD
Pathological hypersecretory conditions (Zollinger-Ellison, where levels of hormone are increased due primarily to gastrinoma tumour of non-beta islet cells in the pancreas)
PPI SEs
generally well-tolerated short term
nausea, ab pain, constipation/diarrhea, flatulence (alteration in intestinal flora due to pH change)
less common: hypergastrinemia, due to rebound secretion of gastric acid if PPI is stopped after short-term use
Misoprostol PK
short half-life