Lecture 6- Bioavailability and volume distribution

Bioavailability (F)

amount of an administered dose of a drug which reaches the systemic circulation intact

Bioavailability fo IV

F=1

Why do oral drugs have less bioavailibility?

first pass metabolism, degredation

AUC

are under the drug conc curve measuring drug that reaches systemic system

What does AUC not tell us?

how the exposure of drug is distributed over time

two drugs can have the same AUC but

have different conc-time profiles

Absolute avalibility

systemic availability after extravascular administration in comparison to IV

relative availability

availability of drug compared to a standard

bioequivilant drug porducts

must have same AUX, Cpmax, and Tmax

dosage regimin

manner the drug is taken in

• how muhc?

• how often?

pharmacokinetics

ADME- body does to drug

drug disposition

drug distribution and elimination

most important pharmacokinetic variables

volume of distribution and the clearance

Cl adn Vd

are INDEPENDANT PARAMETERS

Volume of distribution

theoretical volume that drug occupies in body

A small VD

drug is mostly in extracellular water

a high VD

drug distributes into the tissues

Is vd constant?

yes

what determines VD?

size polarity lipid solubility tissue affinity

Factors impactong Vd and Cl

age bodyweight disease state etc