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Dear All
we want to do pharmacokinetic studyof the some pure herbal compund
which extracted from extract.
I do not know C max of the compund . How we can decide the LLOQ in
plasma ? Or shall i do the first pilot study and on that basis we can
select or shall i have to determine lowest limt of detection of that
compound in plasma.
Thanking you one and all.
PRASHANT
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The following message was posted to: PharmPK
For a quick guideline, you'll need to spike your compound into plasma,
extract, and determine LOD (S/N > 3) and LLOQ (S/N > 10) under your
analytical conditions. There is FDA guidance on that topic. You may
find it in this list's archive.
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Dear members:
Age old (from HPLC days) accepted criteria lower limit of detection
(LOD) is signal/noise = 3 Lower limit of Quantitation (LLOQ) signal/
noise = 5
Ref: Ken Connors, Handbook of HPLC and page 9 of 25 of the FDA
bioanalytical validation guidance.. IMHO it is better to stick with
the established norms rather than trying to tweak them (such as how
to assign values below BQL)
Hope this clarification helps.
Prasad
Prasad NV Tata, Ph.D., FCP
Saint Louis, MO 63134
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The LLOQ is associated with the analytical method and is a
consequence of risk, sensitivity and noise... It has nothing directly
to do with dose.
You can spike plasma with the analyte and determine at what
concentration you get acceptable accuracy and precision. It should
be above the background response of the unspiked plasma.
Once you get to this point, if you need greater sensitivity you can
try different detection modes, eg total ion chromatography with the
smallest column possible. Possbily enhance by using the greatest
injection volume possible or by sample pretreatment ( cleanup and
concentration) ligand binding ought ot be the same, with a
progression from OD to chemiluminescence, reducing the analytical
dilution as much as possible, and perhaps trying a pre-treatment,
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Dear Prashant,
See FDA guidelines for industry: Bioanalytical Method Validation (p.9)
Lower Limit of Quantification (LLOQ)
The lowest standard on the calibration curve should be accepted as
the limit of
quantification if the following conditions are met:
C The analyte response at the LLOQ should be at least 5 times the
response
compared to blank response.
C Analyte peak (response) should be identifiable, discrete, and
reproducible with
a precision of 20% and accuracy of 80-120%.
2. Calibration Curve/Standard Curve/Concentration-Response
The simplest model that adequately describes the concentration-
response relationship
should be used. Selection of weighting and use of a complex
regression equation should
be justified. The following conditions should be met in developing a
calibration curve:
C #20% deviation of the LLOQ from nominal concentration
C #15% deviation of standards other than LLOQ from nominal concentration
At least four out of six non-zero standards should meet the above
criteria, including the LLOQ and the calibration standard at the
highest concentration. Excluding the standards should not change the
model used.
Hope this helps,
Susanne
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