Preparation of injectable suspensions having improved injectability

A method for administering a composition to a host, comprising:

• (a) mixing dry microparticles with an aqueous injection vehicle to form a first suspension wherein the concentration of microparticles in the first suspension is greater than about 30 mg/ml;
• (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 in the range of from about 20 cp to about 600 cp at 20° C.;
• and
• (c) injecting the second suspension into the host through a needle ranging in diameter from 18-22 gauge.

A method for administering a composition to a host, comprising:

• (a) mixing dry microparticles with an aqueous injection vehicle to form a suspension wherein the concentration of microparticles in the suspension is greater than about 30 mg/ml, wherein the aqueous injection vehicle prior to mixing has a viscosity at 20° C. of less than about 60 cp;
• (b) changing the viscosity of a fluid phase of the suspension to be in the range of from about 20 cp to about 600 cp at 20° C.;
• (c) withdrawing the suspension into a syringe;
• and
• (d) injecting the suspension from the syringe into the host through a needle ranging in diameter from 18-22 gauge.

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

• (a) providing microparticles comprising a polymeric binder, said microparticles having a mass median diameter of at least about 10 μm;
• (b) providing an aqueous injection vehicle having a viscosity of at least 20 cp at 20° C.;
• and
• (c) suspending the microparticles in the aqueous injection vehicle at a concentration of greater than about 30 mg/ml to form a suspension, wherein the viscosity of a fluid phase of the suspension is in the range of from about 20 cp to about 600 cp at 20° C., wherein the viscosity of the fluid phase of the suspension provides injectability of the composition through a needle ranging in diameter from 18-22 gauge.

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

• (a) mixing dry microparticles with an aqueous injection vehicle that comprises a viscosity enhancing agent to form a suspension wherein the concentration of microparticles in the suspension is greater than about 30 mg/ml;
• (b) removing water from the suspension;
• and
• (c) reconstituting the suspension with a quantity of sterile water for injection to form an injectable suspension, wherein the quantity of sterile water for injection is sufficient to achieve a viscosity of a fluid phase of the injectable suspension in the range of from about 20 cp to about 600 cp at 20° C. to provide injectability of the injectable suspension through a needle ranging in diameter from 18-22 gauge.