Effects of excipients on the tensile strength, surface properties and free volume of Klucel® free films of pharmaceutical importance

• Glycerol increases, whereas xylitol decreases the free volume of both LF and MF HPC.
• Both xylitol and glycerol increase the tensile strength of MF films.
• The tensile strength of the MF product makes it suitable for pharmaceutical use.
• The surface properties reveal a macroscopically stable film structure.
• All measurements indicate a macroscopically homogeneous film structure.

The physicochemical properties of polymers planned to be applied as mucoadhesive films were studied. Two types of Klucel® hydroxypropylcellulose (LF and MF) were used as film-forming polymers. Hydroxypropylcellulose was incorporated in 2 w/w% with glycerol and xylitol as excipients and lidocaine base as an active ingredient at 5, 10 or 15 w/w% of the mass of the film-forming polymer. The free volume changes of the films were investigated by positron annihilation lifetime spectroscopy, the mechanical properties of the samples were measured with a tensile strength tester and contact angles were determined to assess the surface properties of the films. It was found that the Klucel® MF films had better physicochemical properties than those of the LF films. Klucel® MF as a film-forming polymer with lidocaine base and both excipients at 5 w/w% exhibited physicochemical properties and good workability. The excipients proved to exert strong effects on the physicochemical properties of the tested systems and it is very important to study them intensively in preformulation studies in the pharmaceutical technology in order to utilise their benefits and to avoid any disadvantageous effects.