Extracting the Global Characteristic Time from Partially Sampled Diffusion-Controlled Drug Release Profiles*

Recently, Ignacio et al^1,2 have proposed to use a global (or integral) time ??^* to characterize drug release profiles from hydrogels and porous systems. In fact, it was shown that the time ??^* has remarkable mathematical properties for diffusion-controlled release systems. In practice, most release experiments give access to partial data (i.e., a finite number of data points within a finite time range). Here, we present a simple ”geometrical” method to calculate this integral time from partial release data and compare its performance to that of an alternative method based on empirical fitting functions. More precisely, we test these approaches for a uniformly loaded system where the initial total amount of drug is unknown. We show that fitting functions containing a single time scale (such as the Weibull function) are sensitive to the data sampling method and thus perform very poorly.

¹ Maxime Ignacio, Mykyta V. Chubynsky, Gary W. Slater, Physica A, 486, 2017

² M. Ignacio, G.W. Slater, Physica A, 567, 2021