Osteoarthritis (OA) belongs to diseases with high comorbidity and most frequently concurrent with obesity, diabetes mellitus (DM), hypertension, and other cardiovascular diseases (coronary heart disease, atherosclerosis), gastrointestinal tract diseases, and chronic diseases of the lung and kidney. Irrational treatment of OA in the presence of comorbidity and without considering characteristics of drug interactions leads to a pronounced increase in the number of adverse reactions (ARs) and to aggravation of the course of all concomitant diseases. From this point of view, therapy seems to be relevant when the latter involves drugs that have both symptom- and structure-modifying properties and have a high safety profile.Objective: to compare the safety of alternating and standard treatment regimens with Alflutop® in patients with knee OA.Patients and methods. 130 patients were enrolled in the trial who had Kellgren-Lawrence Grade II–III primary tibiofemoral knee OA with pain intensity on walking ≥40 mm on a visual analogue scale and who needed to take nonsteroidal anti-inflammatory drugs (≥30 days in the previous 3 months). The patients were randomized into two groups: Group 1 was prescribed Alflutop® 1.0 ml intramuscularly (IM) daily for 20 days (a standard regimen); Group 2 was given 2 ml IM every other day (a total of 10 injections) (an alternating regimen). The duration of follow-up was 14 weeks. The safety of Alflutop® was evaluated by the incidence of ARs and serious ARs (SARs) varying in severity according to medical records, laboratory tests, physical examination, assessment of a patient' vital signs, and electrocardiography (ECG). The patients were examined at the beginning, at the end, and 1 month after therapy.Results and discussion. No SARs were recorded during the study period and follow-up. There were 10 ARs in the group of patients receiving Alflutop® in the standard regimen and 19 ARs in the other group (the alternating regimen). All ARs corresponded to mild and moderate severity, were unassociated with the test drug, and resolved by the end of the follow-up. 12-lead ECG identified only clinically insignificant abnormalities in the patients of both groups. Patients without DM displayed no clinically significant increase in glucose levels. Those with DM had no increased glycemia tendency. Biochemical studies in both groups revealed only clinically insignificant abnormalities, the frequency of which was insignificant.Conclusion. This study has confirmed the comparable high safety of Alflutop® in both standard and alternative therapy regimens. It has also shown that the drug has a good safety profile and can be recommended for wide clinical application in any use regimen: 1 ml daily (a total of 20 injections) or 2 ml every other day (a total of 10 injections).