Bioequivalence and Bioavailability Forum

Dear All,

In case of a racemate with equimolar proportions of levo- and dextro- isomers, there exists a different PK of each isomer. Further, levo-isomer is responsible for therapeutic activity where as dextro- is considered to be inactive. Both the isomers are well detectable in biological matrix.

With the background of above and considering the current EMEA guideline, chiral assay seems to be mandatory for this case. However, the information about "the exposure (AUC) ratio of enantiomers is modified by a difference in the rate of absorption" is lacking.

EMEA guideline also states following: If one enantiomer is pharmacologically active and the other is inactive or has a low contribution to activity, it is sufficient to demonstrate bioequivalence for the active enantiomer.

Now my question is: is it acceptable to measure only active isomer using chiral assay and present the same for BE assessment? or should inactive isomer be also measured and presented with descriptive parameters?

Please share your views.

Thanks and best regards

Heema Valera