Flashcards in Pharmacokinetics and Pharmacodynamics Deck (109)
Pharmacokinetics explains the effect of the body on a drug. Determines things such as the half-life, onset and duration of effects and dosing.
What four processes are included in pharmacokinetics?
The effect that the drug has on a specific individual.
What three principles are included in pharmacodynamics?
What term describes a specific persons reaction to a drug which may be different than another persons reaction to the same drug
Half-life vs. Half-time
Half life is the duration of effect. So half-life of effect which encompasses all possible active metabolites of the parent compound that may prolong the duration of the parent drug. Time necessary to eliminate 50% of the drug from the BODY.
Half-time- is the how long the parent drug stays in the system. Time necessary for the plasma concentration of drug to decline 50% during the elimination phase. Independent of the dose of the drug administered.
The term used to quantify the amounts of a drug that reach the general system circulation after absorption?
plasma clearance (Cl) is the volume of plasma that is entirely cleared of the drug per unit of time.
So the units are volume/time.
Ke is the rate and takes into account the summation of all routes of elimination for a particular drug.
Vd- volume of distribution (whether the drug stays in the plasma, follows total body water or concentrates in the body tissues).
Explain the basics of compartmental model of the body.
Divides the body into compartments that represent THEORETICAL spaces with calculated volumes.
Describe the basic principle of the two-compartment model.
The body is made up of two compartments. One central and one peripheral.
Describe the central component of the two-compartment model of the body (composed of, receives what % of CO, rate of uptake)
Central component contains the highly perfused tissues (kidney, liver, lungs, heart and brain)
Receives 75% of the CO
Rapid uptake of drug (IV drugs are first introduced into the central compartment, distribute to the second compartment, and then return to the central compartment for clearance)
Describe the peripheral compartment of the two-compartment model of the body.
Large calculated volume.
Extensive uptake of drug.
Fat, muscle, hair, bones, nails.
The rate of transfer between compartments decreases or increases with aging? And is dependent on what organs function?
Mathematically describe the volume of distribution of a drug.
Dose of the IV drug/Plasma Concentration before elimination
What three physiochemical characteristics of a drug influence the volume of distribution? Do they increase or decrease distribution?
1. Lipid Solubility increase
2. Binding to Plasma Proteins decrease
3. Molecular Size decrease
What happens if dosing intervals are less than the elimination half time?
In two half times how much of the drug has been eliminated?
In three half times how much of the drug has been eliminated?
In 4 half times how much of the drug has been eliminated?
In 5 half times how much of the drug has been eliminated?
In 6 half lives how much of the drug has been eliminated?
Following systemic absorption of a drug which tissues receive a large amount of the total dose?
The highly perfused ones.
Heart, brain, kidney, liver.
As the ________ decreases below that in the highly perfused tissues drug leaves the highly perfused tissues.
When drug leaves the highly perfused tissues because of a decrease in plasma concentration where does it go? And what is this called?
less well perfused sites (muscles and fat)
Tissues that accumulate drug preferentially act as a what? to do what? which results in what?
Maintain plasma concentration
Large or repeated doses _______ inactive tissue ______ redistribution. They also prolong the ________ but by how?
duration of action
effects on metabolism rather than distribution
What are the driving forces for diffusional distribution (3)?
Rate of Blood Flow.
Systemic absorption depends on what?
Name two advantages to oral administration and three disadvantages.
1. most convenient
2. most economic
2. Destruction by enzymes or acidic gastric fluid.
3. Irregular absorption with food or other drugs.