*2.1. Materials*

Hydrochlorothiazide (HCT) was a gift from Menarini (L'Aquila, Italy). β-Cyclodextrin (βCD) and hydroxypropyl-β-cyclodextrin (Kleptose HP, HPβCd) were kindly donated by Roquette (Lestrem, France). Amorphous randomly methylated-β-cyclodextrin (RAMEB, average MS 1.8) and hydroxyethyl-β-cyclodextrin (HEβCD, average MS 1.0) were a gift from Wacker-Chemie GmbH (Munchen, Germany). Sulfobutylether-β-cyclodextrin (SBEβCD) Dexolve® was gifted from CycloLab (Budapest, Ungary). Sepiolite was from Vicalvaro (Spain) (SV); attapulgite (Pharmasorb colloidal, PHC) was from BASF, and bentonite (or smectite) (VeegumHS, VHS) was kindly gifted by Vanderbilt Minerals (USA). Magnesium stearate and polyvinylpyrrolidone (PVP K 30) were obtained from Sigma-Aldrich Chemie GmbH (Steinhelm, Germany). Sodium starch glycolate (Explotab®) was from JRS Pharma (Rosenberg, Germany). Tablets of HCT commercially available in Italy (Esidrex®) containing 25 mg of drug were from Novartis Farma Spa (Varese, Italy). Other chemicals and solvents were of reagent grade and used without further purification.
