## AUMC ⇒ MRT [PK / PD]

BE-proff,

» […] I can't catch the idea why AUMC is required?

In the BE-context you generally don’t need it at all. It’s only an intermediate step in calculating MRT. Who asked for it?

» Can anybody explain me?

We can see plasma profiles as the result of a stochastic process (drug molecules are absorbed, distributed, and metabolized/excreted). At any given time point a certain fraction is in the circulation. Hey, that’s a

Distributions can be described by ‘statistical moments’

» […] I can't catch the idea why AUMC is required?

In the BE-context you generally don’t need it at all. It’s only an intermediate step in calculating MRT. Who asked for it?

» Can anybody explain me?

We can see plasma profiles as the result of a stochastic process (drug molecules are absorbed, distributed, and metabolized/excreted). At any given time point a certain fraction is in the circulation. Hey, that’s a

*statistical distribution*!Distributions can be described by ‘statistical moments’

\(S_0=\int f(x)dx\)

\(S_1=\int x\cdot f(x)dx\)

\(S_2=\int x^2\cdot f(x)dx\)

**A**rea**U**nder the**M**oment**C**urve). In PK \(\small{x=t}\) and \(\small{f(x)=C}\). We need the AUMC to calculate the MRT (Mean of Residence Times), which is for- iv bolus

MRT = AUMC / AUC

- and for infusion (of length t
_{inf})

MRT = AUMC / AUC – ½t_{inf}

*S*_{2}is rarely used (for the calculation of the ‘Variance of Residence Times’): VRT =*S*_{2}/*S*_{0}– (*S*_{1}/*S*_{0})^{2}. MRT and VRT are the coordinates (x|y) of the ‘center of gravity’ of the profile. Try it: Plot a PK-curve on cardboard and stick a pin through x|y. Makes a nice children’s wind wheel.—

Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮

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*Dif-tor heh smusma*🖖Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮

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### Complete thread:

- Why do we need AUMC? BE-proff 2015-11-02 14:24 [PK / PD]
- Why do we need AUMC? mittyri 2015-11-02 14:44
- Do we need MRT? d_labes 2015-11-02 14:55

- AUMC ⇒ MRTHelmut 2015-11-02 15:13
- AUMC ⇒ MRT BE-proff 2015-11-02 19:18
- AUMC ⇒ MRT yjlee168 2015-11-02 19:43

- AUMC ⇒ MRT BE-proff 2015-11-02 19:18

- Why do we need AUMC? mittyri 2015-11-02 14:44