For supersaturation tests drug loaded extrudates were weighed in equivalents resulting in a total 10 g/L drug concentration in 1 mL phosphate buffer solution (pH = 6.8) (Ph. Eur.) in 1.5 mL Fisherbrand microcentrifuge tubes (Fisher Scientific, Vantaa, Finland). The samples were incubated at 37 °C and mixed at 1100 rpm in a thermomixer (Eppendorf, Hamburg, Germany).