[Studies on spray of niclosamide ethanolamine salt. I. development and effect assessment of spray of niclosamide ethanolamine salt].

Objective: To develop a spray of niclosamide ethanolamine salt for prevention of bovine from Schistosoma japonicum infection, and explore its characteristics and effect.

Methods: The solubilizers, penetrating agents, emulsifiers were screened, and the spray of niclosamide ethanolamine salt was formulated according to the screening results. The niclosamide ethanolamine salt was determined by using a HPLC technique, and the stability was observed. The preventive effect of the spray was assessed by in-vitro trials against cercariae and protection trials in mice.

Results: The screened formulation was presented as following: 1% niclosamide ethanolamine salt was dissolved in 18% dimethyl sulfoxide, and then added with 1% azone and 2% span, together with 78% ethanol, to yield a 1% spray of niclosamide ethanolamine salt. The spray appeared golden flowing liquid, with 1% niclosamide ethanolamine salt in content (W/W), pH 7.4-7.8, and good thermal and cold stability. All cercariae died (100%) while exposed to the spray at a concentration of 1.00 mg/L for 2 min, and the similar effect was achieved while exposed to 0.50 mg/L of the spray for 5 min or 0.10 mg/L for 30 min. The spray at concentrations less than 0.05 mg/L had no evident toxicity to cercariae. A volume of 0.5 ml of the 1% spray was sprayed on the abdomen of mice, 1-3 d later, the mice were infected with S. japonicum cercariae on the spraying sites, no mice were infected, with a protection rate of 100%. Five days post-spraying, the protection rate was 40%, and the worm burden reduction rate was 65.87%. Ten days later, all the mice were infected, however, the worm burden reduction rate was 51.98%. The worm burdens on days 5 or 10 post-spraying were significantly lower than those of the control (P < 0.01). The spray exhibited a good preventive efficacy to mice from S. japonicum infection in lab.

Conclusions: The spray of niclosamide ethanolamine salt has stable physical and chemical property, and is a novel liquid preventive agent against bovine schistosomiasis. In addition, it has a rapid activity against S. japonicum cercariae, so can prevent bovine from S. japonicum infection.