Week 7 Pharmacokinetics Flashcards
what is pharmacokinetics
the body’s effect on the drug e.g. absorption
what is API
active pharmaceutical ingredient
what is biopharmaceutics
study of how physicochemical properties of APIs, dosage forms and routes of administration affect rate and extent of API action.
what is pharmacodynamics
what the api does to hte body
what is clinical pharmacokinetics
applying pharmacokinetic data to design safe and effective therapeutic regimens for an individual patient
What does ADME mean
Absorption
Distribution
Metabolism
Excretion
What does ADME determine
resultant API conc in the body
Describe the flow using ADME
API at site of administration is then absorbed into the plasma. This can then move to different tissues or to the site of action causing a clinical effect.
OR
It is metabolized and unchanged api is then excreted
describe how a tablet causes the desired effect
The tablet disintegrates into granules and then further into particles. The api must then Dissolve into solution before it can be absorbed into the blood stream. That is then carried to the site of action to a receptor which triggers a response.
Why is solubility important
Not all api’s dissolve in water well for example the BP describes three catagories
Freely soluble
Slightly soluble
Pratically insoluble
what does freely soluble mean
needs about 1 ml to dissolve 1 gram
what does slightly soluble mean
needs about 1 L to dissolve 1 gram
what does practically insoluble mean
needs more than 10L to dissolve 1 gram
what is solubility
solubility of an api in any solvent at any given temperature rate is a fixed value so its a property of the value itself
what factors affect the rate at which the API dissolves
Physical form of the API e.g. polymorph
Size of the API
Stirring
What do suspensions avoid
disintegration stage; small particles of API in suspension can begin dissolving straight away
What do solutions avoid
avoid both disintegration and the dissolution because the API is already in solution
why are solutions faster acting than solid based ones
avoids both disintegration + dissolution stage and has API already in
why are the not a lot of solutions seen in stock at a community pharmacy
solids tend to last longer in terms of shelf life so they are favored.
What is bioavailability
the fraction of an administered dose that reaches the blood stream
what is bioavailability denoted by
F
what can bioavailability come in the form of
% or fraction or decimal
what is the bioavailability for IV injectibles
F = 1
how do we calculate the bioavailability
Amount delivered divided by the amount given
Why might the amount delivered not be the same as the amount absorbed
immediatly after GIT absorption the API are prone to 1st pass metabolism by the liver leaving a lot of the drug innert. However bioavailability takes this into account.
What are the consequences of a poor bioavailability
need lots of API in the GIT in order for the little that is absorbed to have any action in the body
makes dosage form large and inconvenient
expensive
inefficient
is half life constant
yes
role of the pharmacist in regards to design
to design a dosage form that
gives the desired pharmacokinetic profile
minimally affected by patient to patient variation
is safe and convenient for patients to take
is stable over long periods of time
minimises sides effects of the api e.g. gastric irritation
