Preparation of injectable suspensions having improved injectability

A composition suitable for injection through a needle into a host, comprising:

• microparticles comprising a polymeric binder and an active agent encapsulated within the polymeric binder, the microparticles having a mass median diameter of at least about 10 μm;
• and
• an injection vehicle, wherein the microparticles are suspended in the injection vehicle at a concentration of greater than about 30 mg/ml to form a suspension, wherein a fluid phase of the suspension has a viscosity greater than about 20 cp and less than about 600 cp at 20° C., wherein the viscosity of the fluid phase of the suspension provides injectability of the composition through a needle into a host,
• wherein the polymeric binder is selected from the group consisting of poly(glycolic acid), poly-d,l-lactic acid;
• poly-l-lactic acid, copolymers of the foregoing, poly(aliphatic carboxylic acids), copolyoxalates, polycaprolactone, polydioxanone, poly(ortho carbonates), poly(acetals), poly(lactic acid-caprolactone), polyorthoesters, poly(glycolic acid-caprolactone), polyanhydrides, polyphosphazines, albumin, and casein,
• wherein the injection vehicle comprises a viscosity enhancing agent comprising sodium carboxymethyl cellulose;
• a wetting agent selected from the group consisting of polysorbate 20, polysorbate 40, and polysorbate 80;
• and a tonicity adjusting agent comprising sodium chloride, and
• wherein the viscosity of the fluid phase of the suspension provides injectability of the composition into a host through a needle of medically acceptable size.