Design of controlled-release formulation for ivermectin using silicone.

The purpose of this study was to design a formulation using silicone as carrier, so that release of ivermectin (IVM) can be controlled for a long period of time. The lateral side of a cylindrical matrix-type formulation composed of IVM and silicone was covered with silicone to obtain a covered-rod (CR) formulation. With this formulation, linear release of IVM was obtained. With addition of polyethylene glycol 4000 (PEG), release of IVM was accelerated. In a trial with subcutaneous administration to mice, blood concentration of IVM was maintained within one-order over a period of 3 months. The velocity of release of IVM from CR preparation depended on the change in solubility of IVM by additives, and in the case of a formulation with addition of desoxycholate sodium, linear in vitro release of IVM was observed over a period of 1 year.