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.degree. 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.