PK players

What does the suffix -kinetics mean?

Rate of change

Pharmacodynamics is what the _____ does to the _____ and kinetics is what the ______ does to the ______?

• Drug does to the body

• Body does to the drug

Define clearance

a measure of the body’s ability to eliminate the drug

Define ½ life

A dependent variable reflecting both the clearance and Vd

Define bioavailability

A measure of the site-specific membrane permeability and first pass

Define volume of distribution

A measure of the space available into which the drug may distribute

Define absoprtion

A measure of how fast a drug crosses membranes and enters the general circulation

CL is used to set what?

The dosing rate

½ is used to set what

dosing interval

bioavailability defines the what?

dose adjustment

Vd is used to set what?

loading doses

Absorption tells us what about the drug?

how fast the drug enters the general circulation

Define therapeutic index (TI)

range of concentrations where we have acceptable pharmacologic responses to a drug without unwanted side-effects

Define target concentration

The average concentration we are aiming for with a dosing regimen

Value that is within the TI and set by prescriber

The volume of plasma cleared of drug per time and is used to set the dosing rate together with target concentration

clearance

the time it takes to eliminate half of the drug per time and is used to set the dosing rate together with TI to set the dosing interval of the drug

half life

the fraction of drug entering the general circulation and used to adjust the administered dose

bioavailability

CL can vary with what?

• size

• age

• genetics

• disease

• co-treatment

• diet

Clearance is measured from __________

area under the plasma concentration time curves

Vd can vary with what?

• size

• protein binding

• adipose tissue

Vd is measured how?

using initial concentration after IV administration or from half-life and CL

This component is dependent on CL and Vd and is assessed using plasma concentration time data

½ life

(F) can vary with what?

• CL

• formulation

• food

• route of administration

• co-administration of other drugs

• transporters

• rate of absorption

How is (F) determined?

comparing AUC after administration of a dose relative to AUC from IV dose

Absorption rate can vary with what?

• formulation

• diet

• GI motility

• route of administration

• posture

• activities

• co-administration

How is absorption rate constant measured?

From plasma concentration time curves

Units of CL

• mL/min

• L/hr

Units of ½ life

• mins

• hrs

• days

Units of bioavailability

• fraction

• per cent

Units of Vd

L

Absorption rate constant units

• min ^-1

• hr^-1