## Potency correction: Rather why than when [Regulatives / Guidelines]

Hi Hötzi,

» let’s consider the basics. We have a set of two equations
1. AUCT = ƒT·DT/CLT
»
2. AUCR = ƒR·DR/CLR
which consist of eight variables. We are interested to compare the bioavailabilities or ƒTR (not the individual values ƒT and ƒR), reducing the variables to seven.

You are on the right track. I think this was largely an answer to a question I didn't ask, and not answer to the question I asked. I believe I once again perhaps did not explain myself properly enough.

I will try and use your own language:
AUCT/AUCR=(fT/fR)(DT/DR)(CLR/CLT)
where we will assume CLT=CLR, so
AUCT/AUCR=(fT/fR)(DT/DR) or
(DR*AUCT) / (DT*AUCR) = fT/fR or

(DR/DT)*(AUCT/AUCR)=fT/fR

This multiplication by the dose ratio is essentially what the potency correction achieves. You can rearrange that also in another outright horrible fashion:

(AUCT/DT) / (AUCR/DR) = FT/FR

Ouch. Potency correction is the wonderful tool I can use to prove that 5x250 mg Schützomycin tablets are bioequivalent to 1x250 mg Schützomycin . Let us for the purpose of this discussion leave out non-linear kinetics etc.

I could be wrong, but...

Best regards,
ElMaestro

No, of course you do not need to audit your CRO if it was inspected in 1968 by the agency of Crabongostan.