Bioequivalence and Bioavailability Forum • Eyeball-PK

Eyeball-PK [NCA / SHAM]

posted by Helmut – Vienna, Austria, 2012-07-11 17:47 (4663 d 18:07 ago) – Posting: # 8933
Views: 24,192

Dear Hiren!

❝ Ok, I need little bit further clarification and for that please concider these properties of a drug (BE study...NCA used)

❝

❝ 1. Drug is a pure solution and nothing like precipitation and all. I mean pure solution form

The fact that your drug is completely in solution doesn’t prevent precipitation in the body. Blood ≠ Ringer’s solution. Apart from a small increase after end of infusion due to analytical variability sometimes you see an increase which may last for more than an hour – that’s an indication of precipitation. You have to inspect the individual profiles and should not assume “this is an infusion, therefore C_max/t_max = end of infusion”.

❝ 2. Instantaneous distribution happens in your central compartment.

❝ 3. No compartmental specific distribution or in and out from any compartment

❝ So if 1, 2 and 3 are correct. Cant we concider that elimination phase is only working phase as soon as infusion is over?

Still you have to check #1. So my answer is only a “conditional yes”. ;-)

❝ And if yes since you are knowing from what time the elimination phase has started it would be a bias if you are selecting 3 or 4 points from bottom of the curve to find Kel irrespective you are going for R2 or mannual.

Do we really know that? Check the profiles.

❝ One has to select all the time point in the elimination phase characterization.

Well – at least for i.v. as many as possible since analytical error is inverse proportional to concentration.

❝ In extra-vascular since we are unable to differentiate from where the elimination starts we start from bottom of curve and go up.

Yep.

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Complete thread:

Methods for calculation of half lives d_labes 2008-02-01 14:58 [NCA / SHAM]
- Methods for calculation of half lives Helmut 2008-02-01 16:59
  - Methods for calculation of half lives Ohlbe 2008-02-02 23:00
    - Minimum AIC?! Helmut 2008-02-03 13:49
      - G (Kinetica) = R²adj (WinNonlin) Helmut 2008-02-04 01:12
  - Methods for calculation of half lives d_labes 2008-02-04 16:43
    - MAIC and beyond... Helmut 2008-02-04 17:49
- TTT method Helmut 2008-05-10 13:56
  - TTT method d_labes 2008-05-16 09:12
    - TTT method Helmut 2008-05-16 17:21
      - TTT method d_labes 2008-05-23 15:43
        
        TTT method hiren379 2012-07-11 11:11
        
        TTT method Ohlbe 2012-07-11 11:37
        
        TTT method hiren379 2012-07-11 11:44
        
        TTT method Ohlbe 2012-07-11 12:16
        
        TTT method hiren379 2012-07-11 12:53
        
        Eyeball-PK Helmut 2012-07-11 14:37
        
        Eyeball-PK hiren379 2012-07-11 15:28
        
        Eyeball-PKHelmut 2012-07-11 15:47
        
        Eyeball-PK hiren379 2012-07-11 16:24