Preparation of injectable suspensions having improved injectability
Injectable compositions having improved injectability. The injectable compositions include microparticles suspended in an aqueous injection vehicle having a viscosity of at least 20 cp at 20° C. The increased viscosity of the injection vehicle that constitutes the fluid phase of the suspension significantly reduces in vivo injectability failures. The injectable compositions can be made by mixing dry microparticles with an aqueous injection vehicle to form a suspension, and then mixing the suspension with a viscosity enhancing agent to increase the viscosity of the fluid phase of the suspension to the desired level for improved injectability.
1 . A method for preparing a composition for injection, comprising:
(a) mixing dry microparticles with an injection vehicle to form a first suspension, wherein said injection vehicle comprises a viscosity enhancing agent, a wetting agent, and a tonicity adjusting agent, and wherein said microparticles are suspended in said injection vehicle at a concentration of more than 300 mg/ml and up to 400 mg/ml to form the first suspension; and
(b) mixing the first suspension with a viscosity enhancing agent to form a second suspension, wherein the viscosity enhancing agent increases viscosity of a fluid phase of the second suspension to be greater than 20 cp and less than 600 cp at 20° C., wherein the viscosity of the fluid phase of the second suspension provides injectability of the composition through a needle ranging in diameter from 18-22 gauge.