Objective: to evaluate the effectiveness of intranasal application of colloidal silver solution Deflu^® Silver Nose in the complex treatment of moderate-to-severe acute viral rhinosinusitis for the prevention of bacterial complications. Materials and methods. A prospective controlled study was conducted involving 50 patients aged 18–65 years with moderate-to-severe acute viral rhinosinusitis. Patients were evenly divided into two groups: the study group (n=25) received standard treatment with the addition of Deflu^® Silver Nose, while the control group (n=25) received only standard treatment. The observation period was 14 days. Efficacy was assessed using the SNOT-22 scale and a ten-point visual analog scale for nasal symptoms. Results. On day 7 of treatment, the Deflu^® Silver Nose group showed significantly lower scores for nasal congestion (2.2±0.6 vs. 4.0±0.5, p<0.0001), facial pain/pressure (0.9±0.5 vs. 1.9±0.6, p<0.0001), and olfactory dysfunction (1.9±0.6 vs. 2.9±0.5, p<0.0001) compared to the control group. The total visual analog scale score was statistically lower in the study group (14.1±1.4 vs. 16.1±1.3; p<0.0001), as was the SNOT-22 score (19.4±7.0 vs. 24.5±6.1; p<0.01). The combined efficacy index was 62.3±5.9% vs. 54.6±5.4% (p<0.0001), and the effect stability index was 46.4±6.6% vs. 36.0±7.8% (p<0.0001). No adverse effects or bacterial complications were registered in either group. Conclusions. Intranasal application of colloidal silver solution Deflu^® Silver Nose in the complex treatment of moderate-to-severe acute viral rhinosinusitis is a safe and effective method for improving clinical symptoms and preventing bacterial complications, allowing its recommendation for inclusion in treatment protocols for this pathology.