SUMMARY
Recently different excipients, including colouring agents, are often used to give a marketable appearance and improve the consumer characteristics of drugs. Usually they are applied in the composition of medicines for internal use (tablets, capsules, syrups, troches, lozenges, etc). Synthetic azo dyes – a group of compounds obtained by the coupling reaction of sulfonaftilamines and diazotised sulfoanilines with aromatic or heterocyclic phenols are the most widely used in the pharmaceutical practice. Compounds of this group give bright, easily reproducible colours, they are resistant to the light, oxidants, reducing agents, pH changes and less sensitive to different types of technological impact. Synthetic azo dyes are poorly absorbed from the intestines after intake, but they can form ion associates with salts of organic bases, including with drugs, and it may alter their bioavailability. The aim of our work was to determine the partition coefficient of the ion associate of a synthetic food azo dye carmoisine with the medicinal substance chlorpheniramine maleate in the water-chloroform system and to study the stoichiometric ratio of the components in this ion associate. The partition coefficient in the water-chloroform system has been determined spectrophotometrically. It is 3.44, indicating that the ion associate is more soluble in water than in chloroform. The stoichiometric ratio of carmoisine and chlorpheniramine maleate in the resulting ion associate has been determined by HPLC, and it is 1:2.