Drug Absorption and Oral Route II Flashcards
What kind of drugs form ion pairing with other ions in the GI tract to form absorbable species (neutral) which have high lipid solubility?
Ionized (quaternary ammonium compounds)
What are some physiochemical factors that affect absorption?
- Chemical stability
- Ion pairing
- Hydration
- Formation of micelles
- Complexation
Chemical complexation of a drug with other components of the GI tract can (increase/decrease) solubility and reduce absorption
Decrease
In dissolution-rate limited process, the absorption of these drugs depends on what?
Amount of drug in solution
What is the rate-limiting step in dissolution-rate limited processes?
Getting the drug in solution
What is the rate-limiting step in absorption-rate limiting processes?
Getting the drug across the membrane
What word describes: Process by which a drug particle dissolves and goes into a solution.
Dissolution
What is the first step of dissolution?
Form the diffusion layer on surface
What is the second step of dissolution?
Pass throughout the dissolving fluid + ensure absorption
What is the name of the law that describes the dissolution rate?
Noyes-Whitney equation
How can you increase dissolution?
- Increase dissolution rate constant (k)
- Increase SA
- Increase saturated solubility..?
What are some issues with increasing SA to increase dissolution?
- Particles may have wetting issues
- Powders may entrap + absorb air
- Fine particles could generate poor flow of powders
In general, the ____ form with the lowest free energy is the most stable polymorph
crystal
What do amorphous structures typically revert back to?
Crystalline state over time
What is the main similarity and difference between crystal form and polymorph?
Polymorph has the same chemical structure, but different physical properties
