Pharmaceutics + PK GI Flashcards
What is the active ingredient in Gaviscon?
Bicarbonate
Carbonate
What happens with antacids?
Carbonate reacts with H+ to form bicarbonate
Bicarbonate reacts with H+ to get carbonic acid
Carbonic acid is converted to H2O + CO2
Then released as CO2 (g) from body
What are hydroxybenzoates used as?
Preservatives
What happens with Gaviscon?
Polymers = form long chains
BUT requires pH 1
Sodium alginate reacts to form low solubility
Excess ions with X to form low solubility = common ion effect
What does Gaviscon mimic?
Oesophageal sphincter
= blocks so acid won’t come up
In what order do you try the drugs?
Antacid
H2-anatgonists
PPI
What happens with Ranitidine?
H2-anatgonist
Substitute for histamine
Increase pH well on first day
BUT not sustained as week goes on
= when inhibits cell makes more receptor = now same amount of drug BUT increased receptors
What happens with Pantoprazole?
PPI
Binds to proton pump = can’t work again
More effective BUT takes longer to reach MAX effect
Why are things formulated with enteric coat?
Protect body
Protect drug
Protect target
What is essential for enteric coat?
COOH
What happens to unionised polymer of enteric coat?
Remains locked in = NO H2O
BUT increase pH, COOH ionised = H2O attracted inside of mesh = expansion = crystalline drug dissolution
What does biopharmaceutical classification system do?
Rank drugs based on vol required to dissolve drug
What is Class 1?
Biopharmaceutical classification system
High solubility
High permability
What is Class 2?
Biopharmaceutical classification system
Low solubility
High permability
What is Class 3?
Biopharmaceutical classification system
High solubility
Low permeability
