Rheology-based substantiation of a gel-former choice for vaginal gel

Abstract

Gel is an effective semisolid dosage form for local application, which is a single, two- or multiphase system with a liquid dispersion medium whose rheological properties are due to the presence of gel formers at relatively low concentrations. The formation of gels is associated with the emergence and strengthening of bonds between the macromolecules of polymers with the formation of a spatial grid, which holds up to 99% of the total volume of the solvent in the intervals. Gels possess certain rheological and structural-mechanical properties, which include viscosity, plasticity, elasticity and resilience. The strength of the internal structure depends on the nature and ratio of the components of the gel base and is estimated by the yield shear stress and thixotropy, which characterize the state of the system in static conditions, as well as the plastic viscosity, which characterizes the state of the system in dynamic conditions. Rheological parameters also affect such quality indicators of the drug as resistance to destruction, the convenience and ease of application to the surface of the skin, the bioavailability of the active substance, in addition, optimization of the production process can be carried out using data from rheological studies .The study of rheological parameters is important for choosing the mixing speed, temperature regime and determining the critical stages in the industrial production of drugs in the form of gel [2- 5].In the course of rheological research it is necessary to determine such indicators as viscosity, deformation, shear stress. Shear stress is a measure of the intensity of the resistance of the internal forces of elasticity. The yield stress characterizes the ability of the bases and gels to perform some resistance to smearing, the ability to squeeze out of tubes and dispensers of industrial equipment. Therefore, the definition of these indicators is a necessary step in the development of a semisolid dosage form of proper quality.