Mithu
☆    

India,
2019-07-23 07:11

Posting: # 20434
Views: 490
 

 Free and total analyte to be measure in biological fluid [Bioanalytics]

Dear All,

please let me know under what condition, free and total analyte needs to be measured in biological fluids? this is especially became more difficult to us when label speak about free and total analyte but where the OGD does not speak about the same.

Hope i am clear with my question.

Regards

Mithu
Helmut
★★★
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Vienna, Austria,
2019-07-23 11:06

@ Mithu
Posting: # 20436
Views: 446
 

 Free and total analyte

Hi Mithu,

» please let me know under what condition, free and total analyte needs to be measured in biological fluids?

Please define your terms.

Are you referring by “free” to the fraction which is not protein-bound? Protein-binding is caused by Van-der-Waals forces which will be broken in any sample preparation (SPE, LLE, protein precipitation). Hence, what we measure is always the total analyte. If you are interested in protein-binding (not relevant in BE) go with equilibrium dialysis, ultrafiltration, ultracentrifugation.

Or are you talking about a liposome-encapsulated drug (unencapsulated and encapsulated fractions)? The EMA and the FDA require both (examples: EMA, FDA*).


  • At last year’s 3rd GBHI-conference nitpickers pointed out that the term “free” should not be used when “unencapsulated” is meant.

Cheers,
Helmut Schütz
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Mithu
☆    

India,
2019-07-23 13:32

@ Helmut
Posting: # 20437
Views: 424
 

 Free and total analyte

» Please define your terms.

Free analyte available in systemic Vs. Conjugated drug.

» Are you referring by “free” to the fraction which is not protein-bound?

Yes.

Here i am talking about Scopolamine Patch 1/72 hrs. The label is talking about free as well as total Scopolamine (free + conjugated analyte). SBOA contains study which was approved in 2015 does not contain any bifurcation of total or free Scopolamine measurement.

As per my understanding, when half life is less i.e. <10 hrs and there is no major protein bounding, i believe what we are measuring is beyond the category of free or conjugated. As i believe, when there is a higher amount of protein binding, half life would be also high i.e. >20 hrs and more and clear information about drug conjugation should be defined.

please correct me if my understanding is not correct.

In such cases, where we have to measure free and total analyte, analytical methodology would also be different and must contain different extraction method to detect free as well as conjugated analyte.

Here label says metabolize profile of Scopolamine is not fully characterized.

Hope i could put my point in current manner and properly.

Regards,

Mithu
nobody
nothing

2019-07-24 10:45

@ Mithu
Posting: # 20439
Views: 385
 

 Free and total analyte

protein binding has nothing to do with "conjugation" (typically used for phase 2 biotransformation reactions), as Helmut pointed out above it's only quickly reversible "binding" to protein components of blood/plasma.

Kindest regards, nobody
Ladi
☆    

Thailand,
2019-07-29 13:15

@ Mithu
Posting: # 20463
Views: 255
 

 Free and total analyte

Hi Mithu,

» » Are you referring by “free” to the fraction which is not protein-bound?
»
» Yes.
»
» Here i am talking about Scopolamine Patch 1/72 hrs. The label is talking about free as well as total Scopolamine (free + conjugated analyte).

My understanding with conjugated analyte in this case is Scopolamine + 'a moiety' such as glucuronide moiety. Scopolamine dose have sulfate conjugated and glucuronide conjugated forms as its metabolites. So in this case free Scopolamine is the measurement of unconjugated Scopolamine only while total Scopolamine is the measurement of free Scopolamine + deconjugated Scopolamine (after some hydrolysis reactions). Similar case with Ezetimibe. I think nothing have to do with protein binding here.

This journal talks about the free and conjugated Scopolamine>> https://www.ncbi.nlm.nih.gov/pubmed/18970269


Making sense?
Ladi
Mithu
☆    

India,
2019-08-03 10:41

@ Ladi
Posting: # 20468
Views: 184
 

 Free and total analyte

» This journal talks about the free and conjugated Scopolamine>> https://www.ncbi.nlm.nih.gov/pubmed/18970269

thank you.

Regards,

Mithu
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