Development of Solid SEDDS, IV: Effect of Adsorbed Lipid and Surfactant on Tableting Properties and Surface Structures of Different Silicates

To compare six commonly available silicates for their suitability to develop tablets by adsorbing components of liquid lipid-based drug delivery systems. The tabletability of AerosilA (R) 200, SipernatA (R) 22, SylysiaA (R) 350, ZeopharmA (R) 600, NeusilinA (R) US2 and NeusilinA (R) UFL2 were studied by compressing each silicate into tablets in the presence of 20% microcrystalline cellulose and measuring the tensile strength of tablets produced. Three components of lipid based formulations, namely, CapmulA (R) MCM EP (glycerol monocaprylocaprate), CaptexA (R) 355 EP/NF (caprylic/capric triglycerides) and CremophorA (R) EL (PEG-35 castor oil), were adsorbed individually onto the silicates at 1:1 w/w, and the mixtures were then compressed into tablets. The SEM photomicrographs of neat silicates and their 1:1 w/w mixtures (also 1:2 and 1:3 for NeusilinA (R) US2 and NeusilinA (R) UFL2) with one of the liquids (CremophorA (R) EL) were recorded. Neat AerosilA (R) 200, SipernatA (R) 22 and SylysiaA (R) 350 were non-tabletable to the minimum acceptable tensile strength of 1 MPa, and they were also non-tabletable in presence of liquid. While ZeopharmA (R) 600, NeusilinA (R) US2 and NeusilinA (R) UFL2 were tabletable without the addition of liquids, only NeusilinA (R) US2 retained acceptable tabletability with 1:1 liquid. The SEM images of silicate-liquid mixtures indicated that, except for NeusilinA (R) US2, much of the adsorbed liquid distributed primarily at the surface of particles rather than inside pores, which hindered their compaction into tablets. Among the six silicates studied, NeusilinA (R) US2 was the only silicate able to produce tablets with acceptable tensile strength in presence of a lipid component at 1:1 w/w ratio due to the fact that the liquid was mostly adsorbed into the pores of the silicate rather than at the surface.