zero-order dissolution

If dissolution data has a linear correlation (cumulative mass vs time) that is indicative of zero-order release, is it appropriate to fit a sigmoidal dissolution model?

The IVIVC toolkit in Phoenix allows only 4 choices for dissolution profiles: Hill, Weibull, Double Weibull and Markoid-Banakar.

If a sigmoid model is inappropriate, then how do we move forward to correlation within phoenix without choosing a sigmoid fit?

I am currently stumped on this issue. Could it be that the toolkit is wholly inappropriate for zero-order release rates?

If a model is not required then check the box “use raw data”. Simon.