5301 Bioavailability and Bioequivalence Study Materials

Bioavailability

the RATE and EXTENT to which a drug reaches the systemic circulation unchanged

Synonymous terms to Bioavailability

Biological Availability
Systemic Availability

Parameters we need to represent bioavailability:

1) Peak height (Cmax)
2) Tmax --> Rate
3) AUC --> Extent

Types of Bioavailability

Absolute bioavailability
Relative bioavailability

Absolute Bioavailability

you must use the AUC oral and AUCiv OF THE SAME DRUG:

equation: F=AUC oral/AUC IV

absolute bioavailability numerically can be from 0-1 (F=0-1)

Absolute Bioavailability (% bioavailability)

The absolute bioavailability numerically can be from 0-100 (F=0-100)

%F = (AUC oral/ AUC IV) x 100

True or False:
With absolute bioavailability, sometimes you must normalize the AUcs because you may have to give different doses of the same drug when you give orally or when you give it IV.

True

equation for the "Normalized AUCs for dose, if you have different doses":

F= [AUC oral/oral dose] / [AUC IV/IV dose]

What do you do in the case it is impossible to have IV data?

Use relative bioavailability & compare it w/a standard formulation

Relative bioavailability = [AUC test/test dose] / [AUC std/ std dose]

True or False:
2 formulation of the same drug are bioequivalent when they reach the systemic circulation at the same rate and same extent.

True

Why is bioavailability significant?

1. Different therapeutic effect between patients

2. Comparing different dosage forms of the same active drug