Аннотация:The work was devoted to increasing the solubility of the anthelmintic agent niclosamide (NS). Methods for increasing the solubility of NS were described. Alternative methods to obtaining drugs with NS solubility increased 2 – 12 times were proposed. The cytotoxic effect of the various forms of NS was tested on HeLa tumor cells. It was found that a nanosuspension containing 6.6% NS showed the highest cytotoxic activity. The initial NS substance exhibited the minimum cytotoxic effect on HeLa cells as compared to a microemulsion,microcapsules, a solid dispersion, and a mixed NS:PVP solid dispersion (1:10 ratio). The cytotoxic effect of all dosage forms grew and did not depend on the NS concentration in the studied dosage forms if the incubation period of the tumor cells increased from 24 to 48 h.