2.3.2. Powder Flowability

Powder flowability was determined by the Copley flow-test (Copley Scientific Ltd., Nottingham, UK), evaluating the powder ability to freely flow through a circular orifice of known diameter. The flowability index is given by the diameter (ranged from 4 to 26 mm) of the smallest hole through which the powder falls freely (mean of three determinations).

#### 2.3.3. Powder Compactability

Powder compactability was evaluated according to the Wells method [48]. Briefly, 3 samples were prepared for each carrier, by weighing each time aliquots of 5 g of powder, adding 50 mg of Mg stearate as a lubricant, and mixing in a V-mixer 3 min (samples A and B) or 30 min (sample C). From each sample blend, five tablets (13 mm diameter) were then obtained, by compacting with a hydraulic press 500 mg powder, under 1 ton of pressure for 5 s (A and C) or 30 s (B). After 24 h, the tablets' crushing force (N) was measured (Schleuniger Hardness Tester model 6D, JB Pharmatron, Northampton, UK).

#### 2.3.4. Specific Surface Area

Specific surface area measurements were performed according to the BET (Brunauer-Hemmet-Teller) method using an automated ASAP (Accelerated Surface Area and Pore) 2010 adsorption analyzer (Micromeritics, Norcross, GA, USA) at −196 ◦C. Before analysis, samples were degassed 24 h at room temperature using a VacPrep apparatus (Micromeritics, Norcross, GA, USA).

#### *2.4. Preparation of Liquisolid Systems*

The drug was completely dissolved in the minimum necessary amount of solvent; then the drug solution was put in a mortar, where the mesoporous silica (or clay) powder was gradually added, under mixing, up to obtain an apparently dry powder.
