ka vs. Cmax [Dissolution / BCS / IVIVC]

posted by Helmut Homepage – Vienna, Austria, 2017-06-09 16:35 (2484 d 22:43 ago) – Posting: # 17477
Views: 13,967

Hi nobody,

❝ Hmmm, did anybody try to establish ka as an alternative in BE?


IIRC, it was the other way ’round. Theoretically we are interested in ka, and Cmax (better together with tmax) is only a better accessible surrogate for it. In the early days of BE people tried to estimate ka indeed. For a one-com­partment model Wagner-Nelson or the residual method works. But: Due to error propagation, the estimate is not very robust. For more than one compartment we have only Loo-Riegelman and deconvolution (both requiring IV data and six to ten samples up to ~2×tmax). Difficult. So, people gave up and since then Cmax is the established surrogate metric for the rate of absorption.

❝ Would be fun to see some 100s of old BE-trials re-evaluated based on ka, I guess...


AFAIK, in those ol’ days BE-limits for ka were never defined. Given that Cmax is less sensitive (influenced by AUC) – even if one has data to reliably estimate ka – I guess it would be rather difficult to show BE with the common limits.

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