Introduction. The transition of a patient from inpatient to outpatient care is often accompanied by insufficient coordination between medical professionals and pharmacy institutions, which can lead to the patient not receiving necessary information about new prescriptions and potential drug interactions. This increases the risk of adverse effects and reduces the effectiveness of therapy. The exacerbation of comorbidities during hospital discharge requires special attention to polypharmacy issues, where a patient takes multiple medications simultaneously. In such cases, it is important for pharmaceutical workers to be able to objectively assess and predict potential interactions, which will help minimize risks and improve treatment outcomes. The lack of monitoring in the post-marketing period highlights the need for a systematic approach to pharmaceutical support for patients, which will enhance the quality of medical care and reduce financial costs associated with treating complications caused by drug interactions. Objective. To conduct a frequency analysis of drug interactions using antibacterial medications with various substances, as well as a detailed description of interactions and potential consequences during their use in a pharmacy that conducts retail sales and provides preferential dispensing of medications to patients. Materials and Methods. The study was conducted from October 1, 2023, to November 30, 2024. During 33,706 patient visits, 1,688 purchases were identified that could potentially lead to drug interactions. It was assumed that possible interactions with the group of penicillin antibiotics were determined when purchased in a single transaction. That is, it was logical to assume that the patient, making such a purchase, intends to take the purchased medications simultaneously. Results and Discussion. The study identified 1,688 potential drug interactions among 33,706 patient visits, of which penicillin drugs accounted for 6.36% of the total number of interactions and 50.94% of all registered cases. An analysis of 210 combinations of drugs used in conjunction with penicillins showed that 64 interactions are not recommended, 35 interactions have a weak recommendation, and 11 interactions are strongly recommended. These results underscore the importance of a careful approach to prescribing penicillins, considering their frequent use and potential adverse reactions. The implementation of drug interaction monitoring systems in pharmacy organizations and the training of pharmacists can significantly enhance the safety of antibacterial therapy, which is critically important for improving the quality of medical care and reducing risks for patients. Conclusion. The conducted study analyzed the frequency of drug interactions involving antibacterial medications, with a particular focus on penicillin drugs. The results showed that penicillins play a significant role in the practice of prescribing antibacterial therapy in Yekaterinburg, accounting for more than half of all registered drug interactions. Although the share of penicillins in the total number of interactions is 6.36%, this figure highlights the importance of a careful approach to the prescription and use of these medications, considering their potential adverse reactions.