Extravascular Administration Lectures

Question 1

What ADME processes are associated with extravascular administration? Where do these processes occur?

Answer 1

Administration - Into systemic circulation

Distribution - Between circulation and tissues

Metabolism -

Question 2

What is extravascular administration?

Answer 2

Any method of administration wherein the drug does not directly enter the bloodstream (IV).

Question 3

What is the equation for the variation in amount of drug following extravascular administration? What is B?

Answer 3

C = (Be^-kt) - Be^-kat

B is a constant given by certain variables of the drug such as the dose and bioavailability. It provides the units for concentration.

Question 4

What equation can be used to calculate the value of K? What conditions must be met first?

Answer 4

Cterminal = B*e^-kt

We must be observing the elimination phase at a point where the absorption rate equals 0.

Question 5

How do we know when the rate of absorption equals 0 in the elimination phase? Why?

Answer 5

The decline in concentration appears simply linear on semilog paper.

This is because at this point the decrease in conc is modelled by a singular exponential expression and as such will be modelled as a straight line.

Question 6

How do you identify k from the graph?

Answer 6

Identify the linear portion of the curve on semilog paper, calculate the gradient.

Gradient = -k

Question 7

What is oral clearance? How is it different to clearance as we know it?

Answer 7

It describes the combined vale of Cl/F. It is used when there is limited information and the value of real clearance cannot be determined.