Bioequivalence and Bioavailability Forum

Hi Hötzi,

❝ let’s consider the basics. We have a set of two equations

1. AUC_T = ƒ_T·D_T/CL_T
   

   ❝

2. AUC_R = ƒ_R·D_R/CL_R

which consist of eight variables. We are interested to compare the bioavailabilities or ƒ_T/ƒ_R (not the individual values ƒ_T and ƒ_R), 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:
AUC_T/AUC_R=(f_T/f_R)(D_T/D_R)(CL_R/CL_T)
where we will assume CL_T=CL_R, so
AUC_T/AUC_R=(f_T/f_R)(D_T/D_R) or
(D_R*AUC_T) / (D_T*AUC_R) = f_T/f_R or

(D_R/D_T)*(AUC_T/AUC_R)=f_T/f_R

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

(AUC_T/D_T) / (AUC_R/D_R) = F_T/F_R

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.