Bioequivalence and Bioavailability Forum

Hi Murthy,

❝ I have calculated Cτ,ss for a steady state study using the formula

❝ Clast*exp(-Kel(τ-tlast)) for the concentration data on day6.

That’s only necessary if you have deviations from the planned sampling time point.
Otherwise Ĉ_last = C_last since

• τ – t_last = 0
  
• ℯ⁰ = 1…

❝ The dosing interval for the study was 12 hrs and the sampling schedule on day6 is also having 12.00 hr and extended upto 36.00 hrs.

Hhm, generally one would not sample in steady state beyond the dosing interval. If the drug does not show diurnal variations in PK, the target metric for extent of BA would be AUC_0–τ (and no need to sample a second profile on day 6). If the drug has time-dependent PK, the target metric would by AUC_0–24 (i.e., cov­er­ing two pro­files). Generally after the first period one would directly switch to the res­pective other for­mu­la­tion. Since you sampled at 36 hours did you employ a full washout?

❝ I have refered the forum and the lectures given on these topics but i am not able to get conclusion on which data i have to perform BE for Cτ,ss.

Well, you should have stated the relevant PK metrics together with the method(s) of calculation already in the protocol, right? In analogy to AUC look at Ĉ₁₂ or Ĉ₂₄.