Abstract Currently, when health care is provided for the population using methods of pharmacotherapy, the accessibility and range of it are defined by the country’s level of health care. Moreover, a doctor, who prescribes a medication, has to determine how it interacts with other prescription medicines and patient’s already existing diseases. The choice of such medication is extremely difficult if a patient has a large number of illnesses and has already been prescribed medication. This article considers the solution to that issue through the application of the information system based on the expert knowledge, which suggests a reasonable method of pharmacotherapy to a doctor.