Bioequivalence and Bioavailability Forum

Dear ElMaestro!

❝ "Since neither measured nor estimated dissolution percentage should assume negative values there might be a constraint on the error distribution that speaks against using minimisation of sums of squares for estimation of alpha and beta. The applicant should qualify...."

Wonderful! Do you quote from your memory? The style sounds familiar to me (aka ‘old sock’). Next time I fit PK-data to a multiexponential model, I will not state that I use constraints (≥0 for coefficients and ≤0 for exponents).

❝ I am unfortunately too unfamiliar with dissolution (or the Excel solver) but do you have a ref. to a work using the equation you have fitted the data to?

The equation is the CDF of the Weibull-distribution.
Other empirical models in dissolution are the CDF of the exponential (\(\small{y=1-\exp (-\alpha\cdot x)}\), where \(\small{\alpha >0}\)), Higuchi (\(\small{y=\alpha\cdot \sqrt{x}}\)), Korsmeyer–Peppas (\(\small{y=\alpha\cdot \exp (1/\beta)}\)), …
Reference? Hhm, dissolution is not my cup of tea. But have a look at Dissolution Technologies (back issues).

❝ ❝ BTW, Excel is (...) real software.

Yes, Sir!

I’m also unfamiliar with Excel’s solver…