Bioequivalence and Bioavailability Forum

Total drug is usually referred for drugs that are conjugated and unconjugated. In case of highly protein bound drugs (e.g. Warfarin) they report free drug (taken by centrifugation or dialysis) and total (determined after protein precipitation)

Way back in 80s there was an article in Journal of Chromatography, someone published a paper different precipitating agents (methanol, acetonitrile, TCA etc.) and recommended proportions of precipitating agents required for more than 95% protein precipitation and liberating the bound drug.

Plasma + Acetonitrile (1:1)
Plasma + MeOH (1:2)
Plasma + TCA (1:4 I guess)
recommended ACN is the best protein precipitating agent by denaturalization and therefore if you use 1:1 ratio you are certain aliquot contains 100% total drug, being so picky I used two step extraction 1:1 first and on the sediment repeat the precipitation again not to loose any drug in the sediment. Is 2 times sample prep for 1+1 precipitation @x (1:1: plasma: ACN). This was critical while working on Warfarin PK work.

Long wobble for a Dumb question

(Another product that require this kind of analysis is Iron product PK)