A bioerodible composition for delivery of a bioactive agent is the reaction product of a reaction mixture which includes an oxidized dextran solution, and a mixture of solids containing a dihydrazide, a bioactive agent, and optionally a pH adjusting agent in an amount sufficient to achieve a pH of the reaction mixture of 6 or less. The composition may include a release agent for controlled release of the bioactive agent from the composition. A bioactive agent may therefore be administered to a body site in need of the same by providing a first aliquot portion of a reaction mixture comprising an oxidized dextran solution, and a second aliquot portion of a reaction mixture comprising a mixture of solids comprised of a dihydrazide, a bioactive agent, and a solid acid which is present in an amount sufficient to achieve a pH of the reaction mixture of 6 or less, mixing the first and second aliquot portions to form the reaction mixture thereof, and thereafter installing the reaction mixture at the body site and allowing a solidified bioerodible drug delivery composition to be formed thereby in situ.
