Metabolite Formation

After administration of the parent drug, the metabolite AUC is dependent on the amount of the metabolite formed in vivo and the metabolite total body clearance.

AUC(m) =

fm D

CLT (m)

The amount of metabolite formed in vivo cannot be determined from the drug and metabolite data after drug administration only, because fm and CLT(m) are unknown.

The ratio of the metabolite AUC to the drug AUC after drug administration is the ratio of the formation clearance to the elimination clearance of the metabolite.

AUC(m)

AUC
=

fm CLT

CLT (m)
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