Koterwin is a herbal preparation designed for the treatment of urinary tract diseases. It possesses saluretic (salt-excreting), diuretic (urine-excreting), and anti-inflammatory properties. The medicinal plants included in the preparation help dissolve stones (except oxalates). The aqueous infusion of knotweed (Polygonum aviculare L.) and persicaria (Polygonum persicaria L.) contains a complex of flavonoids, tannins, vitamins, and silicon acid compounds. Knotweed infusion has diuretic properties, helps in the expulsion of stones in urolithiasis, has anti-inflammatory effects, and improves the condition of capillary walls. Field horsetail (Equisetum arvense L.) contains water-soluble forms of silicon acid (up to 25%) and its complexes with organic compounds, flavonoids, and triterpene saponins, providing diuretic, hemostatic, and anti-inflammatory effects in bladder and urinary tract diseases. The water-soluble biologically active substances of the field restharrow root (Ononis arvensis L.) include isoflavone glycosides, saponins, triterpene diol (onocerol), tannins, and organic acids, which normalize the tone of smooth muscles, reduce pain during spasms, and increase diuresis.