Bioequivalence and Bioavailability Forum

Hi John,

❝ A dumb question …

You know that there are no dump questions.

❝ Is there a way to find out whether the total drug concentration is measured from a bioanalytical report (no method development report, just bioanalytical and validation reports) if there is no sentence/discussion about that aspect? I read through a report that I was given and I didn't find info on this.

More information, please.
Are you talking about a drug with protein binding? That’s easy. Protein binding is caused by Van der Waals force, which is extremely weak. In a nutshell, in any extraction (liquid-liquid, solid-phase), or protein-precipitation the protein-drug bonds will be practically imme­dia­tely cleaved and therefore, from the extract you get always the total concentration.
If you are interested in the free concentration, you would have to use ultra-filtration or -centrifugation of the same sample, measure this concentration and the total. The protein binding: $$\small{PB(\%)=100\frac{C_\text{total}-C_\text{free}}{C_\text{total}}}$$ Important for new drugs but completely uninteresting in BE.

Liposome encapsulated drugs and their relatives are different beasts.