Bioequivalence and Bioavailability Forum • lag-time

lag-time – another round [Design Issues]

posted by Helmut – Vienna, Austria, 2024-10-19 10:20 (191 d 23:57 ago) – Posting: # 24242
Views: 1,801

Hi Titus,

❝ But clearly in the plot, there is no significant lag time.

You wrote the model without one…

❝ I believe, lag-time can be only observed in normal Conc-time plot. Isn't?

Depends on what you mean by ‘observe’.
By convention in NCA BQLs before t_max are set to zero. Of course, 0 cannot be shown in a log-linear plot. By another convention, t_lag is defined as the time point before the first measurable concentration. Obviously that’s not correct (see also there). The true one is a little later. Another approach¹ is not implemented in any software; roll out your own code. Of course, you can estimate t_lag by a PK model.²

Csizmadia F, Endrényi L. Model-Independent Estimation of Lag Times with First-Order Absorption and Disposition. J Pharm Sci. 1998; 87(5): 608–12. doi:10.1021/js9703333
In all exponential functions substitute $\small{t}$ by $\small{(t-t_\text{lag})}$ with the fitting constraint $\small{t_\text{lag}\ge 0}$ .

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Complete thread:

PK Sampling Time Points - SR Formulation TitusBen 2024-10-17 05:40 [Design Issues]
- PK Sampling Time Points - SR Formulation Helmut 2024-10-17 10:56
  - PK Sampling Time Points - SR Formulation TitusBen 2024-10-18 06:24
    - PK Sampling Time Points - DR Formulation Helmut 2024-10-18 09:16
      - PK Sampling Time Points - DR Formulation TitusBen 2024-10-18 16:45
        
        lag-time – another roundHelmut 2024-10-19 08:20