Dialysates

DIALYSATES, preparations that have undergone dialysis (see) for the purpose of freeing them from crystalloids. Among galenical preparations, many owe their action to high-molecular constituent principles, which include enzymes, proteins, hormones (in organ preparations), as well as alkaloids and glycosides found in plant extracts (in combination with tannic acid). Also, in the production of artificially (synthetically) obtained colloidal preparations, there is a need to free them from crystalloids, mainly electrolytes. 1. Dialyzed extracts. Proposed by Golaz in 1895 on the assumption that crystalline low-molecular compounds do not participate in the therapeutic action of plant extracts. Initially, freshly collected plant juice, mixed with a certain amount of alcohol to prevent fermentation, was subjected to dialysis in dialyzers without access to air. Later, instead of juices, (aqueous) extracts also began to be subjected to dialysis. At the present time, dialysates of ergot, digitalis, and less frequently, corn silk, etc., are used. Ergot extract, prepared generally by the usual method, but then subjected to dialysis before final evaporation (Ergotinum dialysatum), is recommended for parenteral administration, because its solutions do not form precipitates as easily as solutions of ordinary ergotins, which are rich in salts. Aqueous extracts are also subjected to dialysis, and in this way, they replace concentrated decoctions and infusions. 2. Dialyzed colloidal-chemical preparations. The colloidal state of many substances is disturbed by the presence of salts (salting out). Colloidal pseudosolutions, not freed from salts, become cloudy, coagulate, or gelatinize over time (iron albuminate) and often completely lose their therapeutic value (colloidal silicic acid). Greater stability of these preparations can be ensured by removing salts. In large-scale production, dialysis presents significant difficulties. During dialysis, crystalloids diffuse through a semipermeable partition (membrane) into the outer vessel, but at the same time, the washing water penetrates through the membrane into the inner vessel, and the contents of the latter are gradually diluted. Since diffusion from diluted solutions proceeds more slowly, the need arises to evaporate the dialyzed liquid from time to time (in a vacuum), and the dialysis of several liters of a pseudosolution usually lasts for weeks. It is also necessary to take special measures to exclude fermentation, putrefaction, and similar side processes. It is possible to accelerate dialysis by heating (washing with warm water), by using electrodialysis, i.e., simultaneous electrolysis, and by using special dialyzers. In production, dialysis is usually avoided, replacing it with other methods of freeing from salts mentioned below; nevertheless, preparations obtained in this way, which are more or less free from crystalloids, are released by factories under the name of dialyzed (dialysates). Thus, protein materials for peptone are preliminarily boiled with water, which extracts the salts, and such salt-poor material is subjected to hydrolysis; iron albuminate is precipitated and washed with warm water until the salts are removed, and then it is re-peptized. Colloidal sulfur is similarly precipitated with alcohol or alcohol-ether; iron oxychloride is prepared by a method that guarantees a minimal content of electrolytes, and then only the last traces of salts are removed by dialysis. The question of the design of apparatus for rapid dialysis has not yet been technically resolved.