Bioequivalence and Bioavailability Forum

No need to measure carboxylic acid metabolite if u can measure parent drug sufficiently.

Sampling time points can be designed according to PK parameters, BUT recent advancement for detection of clopidogrel in plasma may over rule the sentence" clopidogrel disappers from plasma beyond 2 hours".

Dear Rahul,

❝ ... 300 mg Table.

           ^^^^ SCNR

❝ Active metabolite is non-detectable and as per recommendation we have to measure clopidogrel, so is it required to measure carboxylic acid inactive metabolite?

In the future please state the target country. If you mean the FDA's Draft Guidance it's clear: parent only.
Filipe et al. (2009) is a somewhat strange paper. To be honest I have my doubts whether the analytical method 'worked well' in the lower range. I would not expect to obtain 'clean extracts' by liquid-liquid extraction with n-hexane:ethyl actetate (85:15). Obviously they excluded 4 subjects from the evaluation of AUC_inf. Arithmetic and geometric means of t_½ are far apart with CVs of almost 90%. Unfortunatelly no individual ('spaghetti') plots are given, only arithmetic means of formulations.
I would guess that with a better analytical method the 'terminal phase' seen in this study might disappear. Once you have your own method I would strongly advice to run a pilot study to check the suitability of the method and find optimal sampling time points (also in conformity with FDA's recommendations).