Occupancy, Half Value Duration, Plateau Time in Phoenix/WinNonlin 8 [🇷 for BE/BA]

Hi Astea,

❝ […] an easy way of calculation T50% early and late, T75%, T90% and similar parameters via Phoenix?

I don’t know any method to obtain the intersections in PHX/WNL. As discussed before, starting with release 8.0 the intersection in the decreasing part(s) depends on the selected trapezoidal method (was always lin/log in previous releases). Simple example: $$C(t)=20(e^{-log(2)/4\cdot t}-e^{-log(2)\cdot t})$$
 t    C  0   0.000  0.5 4.198  1   6.818  2   9.142  3   9.392  4   8.750  6   6.759  9   4.165 12   2.495 16   1.250 24   0.312
Calculation of the Occupancy Time (interval where concentrations are above a fixed value) is trivial.
More demanding are the Half Value Duration (HVD, t50%, POT-50), Plateau Time (t75%, POT-25), and their relatives because they depend on the subject’s Cmax. Hence, we need two steps (I used the data of above for subject 1 and ½C for subject 2); example for HVD:
1. Send the data to NCA, map as usual (sort by subject).
User Defined Parameters > Additional NCA Parameters
Parameter: Cmax_2 Definition: Cmax/2
Include with Final Parameters
Parameter NamesUse Internal Worksheet > Include in Workbook:
Set to No for all except Cmax
Rename the NCA object to Preliminary and execute.
2. Send the data to NCA, map as usual (sort by subject).
Therapeutic Response, link to Preliminary.Final Parameters Pivoted
Sort by subject; map Cmax_2 to Lower and Cmax to Upper, execute.
TimeBetween is the HVD. IMHO, TimeLow is only interesting for a fixed limit (Occupancy Time) and if t is the intended τ.
For the linear trapezoidal you should get

subject Cmax  Cmax_2 TimeLow TimeBetween 1       9.392 4.696  16.2089 7.7911 2       4.696 2.348  16.2089 7.7911

and for the lin-up/log-down

subject Cmax  Cmax_2 TimeLow TimeBetween 1       9.392 4.696  16.3383 7.6617 2       4.696 2.348  16.3383 7.6617

Linear interpolation of the intersections will always give a larger interval than the lin/log interpolation.

0.595 to 8.386 = 7.7911

0.595 to 8.257 = 7.6617

I posted an example project at the Certara Forum.

Dif-tor heh smusma 🖖🏼 Довге життя Україна!
Helmut Schütz

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