Study of factors affecting some properties of hydrophilic suppository base

Abstract

The aim. To study the effect of the composition of hydrophilic suppository bases on the physicochemical and osmotic properties of suppositories made from them.
 Materials and methods. The bases were studied with varying compositions of excipients. The microstructure of the bases was evaluated, and the disintegration time and resistance to rupture of suppositories made from them were determined. The kinetics of water absorption and solvent release were studied by dialysis. The content of propylene glycol (PG) and macrogol 400 (M400) in the receptor medium was determined by gas chromatography. The melted bases were studied by rotational viscometry. The electron paramagnetic resonance spectra of spin probes in hydrophilic solvents and bases were obtained; the type of spectrum, isotropic constant (AN), rotational correlation times (τ), and anisotropy parameter (ε) were determined.
 Results. The disintegration times and resistance to rupture of suppositories were determined depending on such factors as the content and grade of poloxamers, the ratio between high molecular weight macrogols and the mixed solvent PG-M400 (60 : 40 % m/m), the ratio of nonionic surfactant and cetostearyl alcohol (CSA) and their total content, water and hard fat content. The introduction of solid fat and a mixture of surfactants and CSA provides the uniform structure of the bases. The mass ratio between surfactants and CSA and their total content are important factors that provide acceptable resistance to rupture and disintegration times for suppositories and reduce water absorption and solvent release. As the temperature decreases from 45 °C to 20 °C, the bases transform from Newtonian liquids to solids. At that time, the microviscosity of the environment of the spin probes increased by about 5 times, but the parameters of their rotational diffusion in solid bases and the mixed solvent PG-M400 are comparable. This indicates the dissolved state of the spin probes in the bases and the absence of the formation of mixed associates from molecules of surfactant and CSA.
 Conclusions. By varying the composition of excipients, the properties of hydrophilic suppository bases can be controlled, significantly reducing their osmotic properties. The active substances in these bases may be in a dissolved state due to the high content of non-aqueous solvents