Bioequivalence and Bioavailability Forum • Error with NCA calculation

Rabbaska
☆

Russia,
2016-01-19 12:53
(3342 d 23:23 ago)

Posting: # 15839
Views: 4,427

Error with NCA calculation [🇷 for BE/BA]

Hello!

I have the data from 2x2x2 crossover trial. The head of file is as needed,

subj,seq,prd,time,conc

After loading the file into R and starting NCA, I get the output:

 -> the subj# 40 (Ref.) in sequence# 1, period# 1,

    λz (kel) cannot be calculated with ARS or AIC.

 subj seq prd drug time conc

   40   1   1    1  0.0 0.00

   40   1   1    1  0.5 0.27

   40   1   1    1  1.0 0.36

   40   1   1    1  2.0 0.42

   40   1   1    1  3.0 0.60

   40   1   1    1  4.0 0.70

   40   1   1    1  6.0 0.49

And so on, for many patients... At the end

Please see above messages. Press Enter to continue...

What does this mean and what to do with it? Is it something with file (I tried to upload the same data with .RData, .csv, .txt and other formats, all in vane) or bear does not like the data? For sure, my friend performed the analysis in Phoenix and had the result.

Helmut
★★★

Vienna, Austria,
2016-01-19 14:16
(3342 d 22:01 ago)

@ Rabbaska
Posting: # 15840
Views: 3,500

λz from two points?

Post reply

Hi Rabbaska,

❝ time conc


❝  0.0 0.00

❝  0.5 0.27

❝  1.0 0.36

❝  2.0 0.42

❝  3.0 0.60

❝  4.0 0.70

❝  6.0 0.49

Your C_max is at four hours and you have only one descending concentration. Even if you would have sampled longer, it is debatable* whether the concentration at six hours should be used (might still be influenced by absorption/distribution). bear requires at least three data points to estimate λ_z.

❝ … and what to do with it?

What does you protocol say? Generally at least three samples are required. Up to you.

❝ Is it something with file (I tried to upload the same data with .RData, .csv, .txt and other formats, all in vane) or bear does not like the data?

The latter.

❝ For sure, my friend performed the analysis in Phoenix and had the result.

Not with the default setting. Of course he/she could have forced PHX to use the last two time points, but

IMHO, it does not make sense.
Would you prefer to report an extrapolated AUC which is 48% of AUC_∞?

Scheerans C, Derendorf H, Kloft C. Proposal for a Standardised Identification of the Mono-Exponential Terminal Phase for Orally Administered Drugs. Biopharm Drug Dispos. 2008;29(3):145–57.

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