L46 - Extrvascular Administration 2 Flashcards
1
Q
Why is k difficult to estimate from the abs phase? Why can it be estimated from the elim phase?
A
- Both absorption and elimination occur
- after tmax, drug available at absorption site is finished
2
Q
What does eqn1 simplify to at the lim phase?
A
Cterminal = B x e^-kt
3
Q
How to estimate k from the elim phase?
A
- from the slope
- extrapolate to t=0, provides B
- use lnCterminal = lnB - kt
4
Q
What is the AUC of the plasma conc vs time profile following an exravascular administration?
A
AUC = DxF / Cl
D - dose
F - fraction absorbed
Cl - clearance
5
Q
What can vol of distribution not be directly obtained from?
A
Oral data
6
Q
When can you estimate V from extravascular data?
A
have Cl and k, Cl = kxV
7
Q
What do you look at to get tmac/time of peak plasma conc?
A
- time reequired for Cmax
- indication of rate of drug abs from dif formulations
- tmax shorter for faster abs, less time to required to reach Cmax
8
Q
What do you look at to get Cmax / peak plasma drug conc?
A
- max plasma drug conc after extravascular admin
- is Cmax enough for therapeutic response?
- is Cmax too high? Toxic?
