[Preparation and Molluscicidal Effect of Chlorosalicylicamide Sustained-release Granules]

To prepare the 5% and 10% chlorosalicylicamide（quinoid-2’, 5-dichloro-4’-nitrosalicylanilide from niclosamide） sustained-release granules （LDS-SRG） and evaluate their molluscicidal effect.

The 5% and 10% LDS-SRG were prepared with screened carriers, surfactants, adhesives, defoamers and lubricants. Their bulk density, water content, repose angle, critical relative humidity, thermal stability and release rate were determined. Spraying method was used to test the molluscicidal effect of LDS-SRG at 1.6 g/m2. Meanwhile, 50% wettable powder of niclosamide ethanolamine salt (WPN) was applied as the positive control at 1.0 g/m2, and dechlorinated water was used as the blank control. The mortality of snails was calculated on days 3, 7 and 14 after administration.

The 5% and 10% LDS-SRG were red brown in color, showed good fluidity, and had bulk density of 0.655 g/ml and 0.594 g/ml, moisture content of 1.15% and 1.28%, repose angle of 39.8° and 39.7°, and critical relative humidity of 64.98% and 61.63%, respectively. Moreover, both showed good thermal stability. The release curve was stable for both 5% and 10% LDS-SRG during day 1 to day 9, and faster release for 5% LDS-SRG than for 10% LDS-SRG. The burst release occurred on days 10 and 15, and the steady release occurred from days 14 and 20 for 5% and 10% LDS-SRG respectively. The snail mortality on day 7 after 5% LDS-SRG 1.6 g/m2 administration and on day 14 after 10% LDS-SRG 1.6 g/m2 administration was both higher than 95%, and higher than that of the 50% WPN 1.0 g/m2 control (P<0.05).

The 5% and 10% LDS-SRG show sustained-release potential and satisfactory molluscicidal effect by spraying, reaching the evaluation standard for molluscicidal agents.