Pharmacokinetics Flashcards
What is the definition of pharmacokinetics?
Study of movement of a drug into and out of the body
What the body does to the drug
What sorts of things can effect drug pharmacokinetics?
Renal function, liver function, GI function, CV function, disease, alcohol intake, pregnancy etc
What is the mnemonic for the pharmacokinetic process?
ADME
Absorption
Distribution
Metabolism
Elimination
Explain the difference between initial plasma concentrations of drugs that are given orally vs given IV
IV drugs - immediate peak plasma concentration
Oral drugs - takes time to be absorbed first so takes longer to reach peak plasma concentration
What is the therapeutic window?
Range of doses in which a therapeutic response is caused without adverse effects
What is Cmax?
Peak plasma concentration
What is Tmax?
Time in which peak plasma concentration (Cmax) is reached
What is bioavailability?
The fraction of a dose which enters the circulation to have an active effect
What is the bioavailbility for an intravenous bolus?
100% (all enters bloodstream)
Note that for other routes, compare amount reaching the body comartment by that route with IV bioavailability
On a plasma concentration/time graph, what equates to the bioavailability?
Area under the curve
How would you calculate oral bioavailability (F) from a graph?
F = Area under the curve (oral) / Area under the curve (IV)
What factors can affect bioavailability?
Drug formulation, age, whether its being taken with food, vomiting, malabsorption, first pass effect
What is first pass metabolism?
Metabolism that occurs before the drug enters the systemic circulation
Where can first pass metabolism occur?
Liver (via portal system)
Gut lumen
Gut wall
Give an example of a drug that undergoes first pass metabolism in the liver
Propanolol, GTN
Give an example of a drug that undergoes first pass metabolism in the gut
Benzylpenicillin, insulin
What two key factors influence drug distribution?
Protein binding and volume of distribution
What is the effect of protein binding on drugs?
They are inactive and can’t be eliminated; most drugs must be free to have a pharmacological effect