Puzzle: Estimation of half life [Surveys]

posted by Helmut Homepage – Vienna, Austria, 2011-07-28 13:38 (5019 d 03:53 ago) – Posting: # 7232
Views: 10,745

Dear D. Labes!

❝ The more interesting question is: What do regulators think?


According to our Master the average time for assessing a BE report is one hour – therefore, nothing.

❝ I never have seen deficiency questions […]



Me not either. :-D

❝ Although I find the fit a little bit strange, […]



Right. Actually the sponsor wants to perform another study and felt that they had too many data points in the previous one (little bit tricky, three drug combo). First I asked for spaghetti plots. Nil. Next for raw data. Received an M$-DOC (actually part of the Appendix to the study report) con­tain­ing SAS-output like the following (one page per profile):
                                                               Plasma
         Age/                               Actual  Blood   concentration
 Site/   Sex/                        Sample  time    vol.      (ng/mL)
Subject  Race   Per. Treat. Sched.   taken  (hh:mm)  (mL)   XXXX    YYYY  Comment
-------------------------------------------------------------------------------------
AA/BBBB 22/M/Ca  1   Tablet pre      Yes    07:37   10.0      BLQ    BLQ
[…]
                            16 h pd  Yes    23:54   10.0   121.33  12.10  late sampl.
[…]

Really handy to be imported into PK software. Next: An Excel-file converted from the SAS-binary. Finally something to work with.

❝ BTW: What is Your eyeball solution for this curve?


Last three data-points. t½ 8.00 h, R² 0.751 (R with 0.867 below the CRO’s cut-off 0.95). Before I start to fit individuals I use to have a look at spaghetti plots. Subjects with higher concentrations consistently showed such a slow phase (t½ >6 h). The quality of fits was sometimes pretty good (R²adj 0.998) and mainly >0.9… Taking the overall-PK into account, I would say that the bad fit of this subject is still justified (haha – I don’t have a R-cutoff…).

I this study residual AUCs were not an issue, but I’m concerned about careless fitting – which might tweak residual AUCs to <20%.

  The only people who see the whole picture
are the ones who step out of the frame.
Salman Rushdie


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