lizhao
☆    

US,
2014-11-06 23:19
(3430 d 06:56 ago)

Posting: # 13835
Views: 5,067
 

 baseline-corrected bioequivalence [General Sta­tis­tics]

If a PD endpoint is an endogenous hormone in human body. The PD metric is the change from baseline after taking the medicine. And it is also the PD metric is a concentration, so I should log-transform it.

Then should I use ln(post_treatment-baseline) as the bioequivalence metric?

Thanks


Edit: Please follow the Forum’s policy. [Helmut]
Dr_Dan
★★  

Germany,
2014-11-07 11:58
(3429 d 18:17 ago)

@ lizhao
Posting: # 13838
Views: 4,110
 

 baseline-corrected bioequivalence

Dear lizhao
You determine the baseline for each individual separately and you get a value X. This value is subtracted from each concentration of your PD-profile and then you log-transform the data ln(C1-X, C2-X, C3-X.....) and perform the ANOVA. So I do not understand what you mean by ln(post_treatment-baseline) as bioequivalence metric.
Kind regards
Dr_Dan

Kind regards and have a nice day
Dr_Dan
Helmut
★★★
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Homepage
Vienna, Austria,
2014-11-07 18:27
(3429 d 11:48 ago)

@ Dr_Dan
Posting: # 13842
Views: 4,063
 

 baseline-corrected bioequivalence

Hi Dan & lizhao,

❝ ❝ If a PD endpoint is an endogenous hormone in human body. The PD metric is the change from baseline after taking the medicine. And it is also the PD metric is a concentration, so I should log-transform it.


Pharmacokinetics may be simply
defined as what the body does
to the drug, as opposed to
pharmacodynamics which may be
defined as what the drug does to
the body.
*


With hormones you may stir up a hornets’ nest. Depending on the hormone you may see an increase, decrease, or even a nasty feed-back loop (i.e., steady state is far from what you would predict from a single dose). Can you be more specific? Which hormone? Population? Single/multiple dose?

❝ You determine the baseline for each individual separately and you get a value X. This value is subtracted from each concentration of your PD-profile and then you log-transform the data ln(C1-X, C2-X, C3-X.....) and perform the ANOVA. So I do not understand what you mean by ln(post_treatment-baseline) as bioequivalence metric.


Subtraction (if we have an increase, of course) is only the first step. I would not log-transform the corrected concentrations. Simply calculate the Cmax / AUC and then log-transform. Important: For AUC don’t use AUCt but include the last triangle if zero is the result of two values >LLOQ.


  • Benet LZ
    Pharmacokinetics: Basic Principles and Its Use as a Tool in Drug Metabolism
    In: Horning MG, Mitchell J (eds) Drug Metabolism and Drug Toxicity
    New York, Raven Press (1984) p199
    ISBN 0-89004-997-1

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