PK Bioavalability and Half-Life (Lecture VII)

Bioavailability

the rate and extent to which a drug administered in a dosage form enters systemic circulation

What is bioavailability described by?

• peak plasma concentration

• time to reach peak concentration

• area under the curve (AUC)

What accounts for the major differences in dosages between species?

Bioavailablity

What does the disposition curve graphically define?

the time course of the drug in the plasma

How do you calculate bioavailability?

F = AUC(oral)/AUC(IV)

Absolute Bioavailability

IV versus non IV

Relative Bioavailability

non-IV versus non-IV

What is the rate of drug elimination (kel)?

fraction of drug eliminated per unit time

WHat is the elimination half-life?

the time required for the body to eliminated one-half of the drug from the blood

How do you calculate t1/2?

t1/2 = 0.693/kel

WHat influences half-life?

• Vd

• Clearance fro plasma

• access of drug to organs

• urinary pH

• species