Flashcards in Pharmacokinetics Biopharmaceutics (1/3) Deck (17):
Study of how physiochemical properties of APIs, dosage forms and routes of administration affect rate and extent of API action
What the API does to the body
What the body does to the API
How does absorption affect the API?
Transports API from site of administration to the plasma
How does distribution affect the API?
Transports API from plasma to the site of action = clinical effect
How does elimination effect the API?
API metabolised and the unchanged API is excreted
List the 4 stages of absorption
Disintegration (from tablet to granules)
Further disintegration (to particles)
Dissolves (API in solution - can be absorbed in the bloodstream)
Carried to site of action
What's the difference between dissolution rate and solubility?
Solubility = fixed value (in a given solvent, at a given temperature)
Dissolution rate = varies with many factors:
Physical form of API e.g. polymorph
Particle size of API
Which stage of absorption does a suspension not undergo?
The disintegration stage - API particles can begin dissolving straight away
Which stages of absorption does a solution not undergo?
The disintegration and the dissolution stages - as API is already in solution (therefore faster acting)
The fraction of an administered dose that reaches the bloodstream (F)
IV = 100% bioavailability
Why do APIs absorbed from the GIT have a lower bioavailability than those administered by IV?
Those administered orally undergo 1st pass metabolism by the liver
What is the formula to calculate bioavailability (F)?
F = amount (route)/amount (IV)
F(IV) = 1 always
List 2 factors about a drug which can stop the API from being absorbed in the GIT
The dosage form does not release the API (so it cannot be absorbed)
The API does not dissolve quickly enough if released so it will pass through the GIT
List 2 consequences of a drug having poor bioavailability
A lot of API is required for the little amount that is absorbed to have an effect (large dosage form, inconvenient, inefficient, expensive)
Patient-to-patient variation in absorption will have a bigger effect than with APIs that are well-absorbed
What is the therapeutic range?
The window between the minimum effective concentration and the maximum safe concentration of a drug