Baseline correction or supra-thera­peu­tic dose [Regulatives / Guidelines]

posted by Helmut Homepage – Vienna, Austria, 2015-09-16 17:16 (3408 d 20:51 ago) – Posting: # 15407
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Hi John,

first of all I agree with Lucas. I don’t get the idea of basing BE on uncorrected data. The EMA’s BE-GL is less ambiguous:

4.1.4 Study conduct
Standardisation

In bioequivalence studies of endogenous substances, factors that may influence the endogenous baseline levels should be controlled if possible (e.g. strict control of dietary intake).
Sampling times
For endogenous substances, the sampling schedule should allow characterisation of the endogenous baseline profile for each subject in each period. Often, a baseline is determined from 2–3 samples taken before the drug products are administered. In other cases, sampling at regular intervals throughout 1–2 day(s) prior to administration may be necessary in order to account for fluctuations in the endogenous baseline due to cir­ca­dian rhythms (see section 4.1.5).

4.1.5 Characteristics to be investigated
Endogenous substances

If the substance being studied is endogenous, the calculation of pharmacokinetic parameters should be per­formed using baseline correction so that the calculated pharmacokinetic parameters refer to the additional concentrations provided by the treatment. Administration of supra-therapeutic doses can be considered in bioequivalence studies of endogenous drugs, provided that the dose is well tolerated, so that the additional concentrations over baseline provided by the treatment may be reliably determined.
If a separation in exposure following administration of different doses of a particular endogenous substance has not been previously established this should be demonstrated, either in a pilot study or as part of the pivotal bioequivalence study using different doses of the reference formulation, in order to ensure that the dose used for the bioequivalence comparison is sensitive to detect potential differences between for­mu­la­tions.
The exact method for baseline correction should be pre-specified and justified in the study protocol. In gen­er­al, the standard subtractive baseline correction method, meaning either subtraction of the mean of in­di­vi­du­al endogenous pre-dose concentrations or subtraction of the individual endogenous predose AUC, is pre­ferred. In rare cases where substantial increases over baseline endogenous levels are seen, baseline cor­rec­tion may not be needed.
In bioequivalence studies with endogenous substances, it cannot be directly assessed whether carryover has occurred, so extra care should be taken to ensure that the washout period is of an adequate duration.

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