Tensile strength and compression of coated pharmaceutical powders

Agglomeration state and migration of drugs in wet granulations during drying

Migration of drugs was studied during drying of wet granules, agglomerated at pendular and funicular state (S(3) and S(4)). Granulating liquids of different viscosity (2.5 and 7.5 mPa s) and drugs and diluents of different solubility and wettability were employed and correlation was sought between distribution of the liquid, wet kneading parameters (torque and liquid consumption S%), solid-liquid interactions (work of adhesion and spreading coefficients) and the migration of drugs. It was found that drug migration, expressed as CV% of its content, was strongly dependent on the type of diluent. Also, the type of diluent exerted the strongest effect on torque and liquid consumption during wet kneading and a significant one on moisture content of the final granulations. Viscosity of the granulating liquid and molecular weight of the binder had no effect on liquid consumption but viscosity had a significant one on drug migration. Significant linear relationships were found between spreading coefficients and the liquid consumption (S%) at the mid-state of funicular agglomeration (S(3)+S(4))/2 or the torque at the capillary state S(5). Migration of drug was remarkably lower for drying in the microwave oven and increased from the pendular (S(3)) to the funicular (S(4)) agglomeration state when drying in conventional oven was applied. Linear relationships were found between migration (CV%) and the spreading coefficient of liquid on solid, lambda(LS), for the low and the high viscosity levels of the granulating liquid, with r=0.965, P=0.05 and r=0.901, P=0.10, respectively. Also, a general linear relationship (r=0.903 and P=0.002) accommodating all experimental data was found between migration (CV%) and the ratio lambda(LS)/viscosity. Drug migration increases with solubility and may become a problem in a range higher than 1 g in 148-400 ml of granulating liquid.

Preliminary evaluation of Leucaena leucocephala seed gum as a tablet binder

The seed galactomannan of Leucaena leucocephala Lam. de Wit var.K-8 (family Leguminosae), a natural polysaccharide, with properties comparable to guar gum, was evaluated as a pharmaceutical binder. Characterization was done using studies of compressibility, micromeritic, and mechanical properties of granules prepared by wet granulation and subsequent studies on compacts, both containing 5% w/w of binder. The seed gum was subsequently used as a binder with a badly compressible material, paracetamol, and studied likewise. The seed gum compared will with standard pharmaceutical binders (starch and polyvinyl pyrrolidone [PVP] K30), at least for properties studied herein.

A consideration of the range and strength of interparticle forces in coated lactose powder

A study has been made of the range and strength of interparticle forces in lactose powder coated with increasing concentrations of paraffins at different temperatures. Marked changes occurred in these forces as the paraffin content was altered and the temperature increased from -10 degrees to +50 degrees C. The strength and range of interparticle forces depended on the mechanical properties of the coating materials and the surface free energy of the coated powders.

Tensile strength and compression of coated pharmaceutical powders: tablets

A study has been made of the tensile strength and compression during tableting of lactose, sodium chloride and calcium phosphate powders after they had been coated with small amounts of stearic acid, polyethylene glycols and polyvinylpyrrolidones. The properties of the systems were measured over a range of temperatures. The tensile strength and the compression behaviour depended not only on the amount and type of the coating material but also on the homologous temperature of processing. The changes in tensile strength have been explained in terms of changes in interparticle separation, changes in interparticle forces and the formation of welded bonds by the coatings. The compression results have been analysed in terms of the Heckel and the Cooper & Eaton equations.