Drugs Flashcards
How do PG’s protect the mucosa?
- inhibit cAMP
- decreased activity of H/K ATPase
- stim production of mucus and bicarb
How is omeprazole processed in the body?
- prodrug
- absorbed and secreted into acidic canaliculi
- acid converts drug by protonation to OM-sulfenamide
What is the active form of omeprazole? Function?
- OM-sulfenamide
- covalently (IRREVERSIBLE) binds H/K ATPase on cell surface (these pumps move to membrane surface when GI system is activated)
- blocks basal and stimulated acid production 80-95%
How is half life of omeprazole affected?
- covalently binds pump so it is irreversible
- elicits effects for turnover time of pump = 24 hours
What protects the oral omeprazole from acid?
enteric coating
What metabolizes omeprazole?
CYP2C19 - metabolized by and inhibit this CYP
What drug interactions should you be concerned about with omeprazole?
any drugs that require acidic environment (ketoconazole) = decreased availability
Two competitive H2 receptor antagonists?
cimetidine, rimetidine - higher potency, 1x a day
How much do H2 blockers reduce acid secretion?
70% - greater effect on basal than stimulated
What may cause a reduction in effect of H2 blockers?
- blocking the receptor results in upregulation of receptor production
Who needs IV PPI?
- patients receiving parenteral nutrition
- if not eating food and still producing acid, need additional protection
- before surgery (aspiration concerns)
- chronic illness
How are H2 blockers excreted? Concerns in elderly?
- renally in inactive and active forms
- decrease dose in elderly with dec renal function
What allows large 1x day dosing of H2 blockers?
large therapeutic window - short half life but can give large doses
3 minor AE’s of H2 blockers?
confusion, depression, hallucinations
What is are 3 additional AE concerns with cimetidine?
- inhibits CYP’s
- dec testosterone binding (gynecomastia, impotence)
- inhibits estradiol hydroxylation (galactorrhea)
- not used much anymore
What is a concern with discontinuing PPI and H2 blockers?
rebound hypersecretion
What kind of drug is dicyclomine?
NON-selective muscarinic receptor antagonist
Uses of dicyclomine?
- IBS (anti-spastic effects)
- NOT anti-acid
What are antacids used for?
rapid relief of dyspepsia and GERD (not effect at treating peptic ulcer disease)
What is the antacid chemical reaction?
acid + antacid – salt + water
What is an adverse effect of bicarb antacids?
- Bicarb is converted to CO2
- belching
What are two effects of Magnesium at high doses?
CNS depression and kidney failure (diarrhea at low dose)
AE of Al at normal and high doses?
- constipation
- dec phosphate absorption
What analog is used to increase mucosal defense?
PGE agonist misoprostol
