SUMMARY
An important step in the complex of research work on the creation of a new drug is the standardization or determination of the quality of the substances used. In Ukraine, a number of regulatory documents on the standardization of APIs and finished medicines, harmonized with the documents of the European Union are put into action.There are number of documents regulating the registration of API, requirements for their quality and recommendations for the development of specifications for active substances.Aim. To develop a methodological approach to the standardization of substances based on uridine and cytidine used as active components for new combined medicines in the form of injection solution and capsules. As well as carrying out a complex of works to determine the set and criteria of quality indicators, the choice or development of methods for their control for inclusion in the specifications.Results. To establish the sequence of actions in the development of specifications for APIs, algorithms have been developed for determining the required set of indicators for specifications, taking into account the type of dosage form and grouping these indicators by type, depending on the availability of standardized methods for their control. Eligibility criteria were established and methods were verified for indicators for which there are standardized methods that do not require changes – these are “Description”, “Heavy metals”, “Residual amounts of organic solvents (ethanol)”. For the indicators “Identification”, “Solution transparency”, “Solution color” and “pH”, the existing unified methods are refined and criteria were established.