Physicochemical aspects of therapeutic effect of enterosorbents (theoretical research)

Abstract

Active promotion of enterosorbents to the market outruns thorough study of the mechanisms of their therapeutic effect. The consumers and even many specialists have a simplified view of the only role of the enterosorbents to fix and remove toxins, that is, act as a "cleaner" of the body. The aim of this paper is to reveal the importance of physicochemical factors for the therapeutic action of enterosorbents. These factors include: (i) electrostatic charge of sorbent surface; (ii) pore size; (iii) accessible area of surface; (iv) hydrophilic-hydrophobic balance of surface; (v) ion exchange properties; (vi) capability to structure water. Mentioned factors can be estimated quantitatively using such methods as electrophoresis, gas chromatography, photon correlation and 1 Н NMR spectroscopy, volumetric analysis, etc. However, in pharmaceutical practice, it is more convenient to characterize the enterosorbent by its capability to adsorb some test substances. To examine the above factors, we use oppositely charged dyes methylene blue and congo red, ions of Zn 2+ , gelatin, phenol and amino acid tryptophan. By the help of this approach we have characterized various types of charcoal, nanosized fumed silica (Atoxil), porous Syloid ® 244FP, hydrophobic Aerosil ® R972, silica gel, Enterosgel, fumed alumina, Smecta ® , zeolites, kaolin, any derivatives of cellulose, lignin and other materials. To study the interaction of enterosorbents with the intestinal mucosa, a gel of eye vitreous humor was used as a model. As a result, we concluded that nanosized silica might be considered first of all as enveloping agent, the main mechanism of action of which is interaction with glycoproteins of the intestinal mucosa. Consequently, two therapeutic effects are realized: (1) difficulty forms for diffusion of pathogenic substances through the mucosa that leads to decrease in their absorption; (2) antidiarrheal effect due to protecting mucosal receptors from the adhesion of microorganisms and impact of microbial toxins. Taking into account that the intestinal mucosa throughout its extent, in the pH range from 6.0 to 9.0, is negatively charged, this interaction for silica occurs with the overcoming of electrostatic repulsion. Therefore, the enveloping power of silica is less than that of alumina containing preparations which in the intestine have a positive charge. Generally speaking, the absorbing mechanism of healing action can only be applied to highly porous sorbents such as charcoal, zeolites, silica gel, Syloid ® 244FP, etc.