A system is described for long-term controlled release delivery of a drug or a therapeutic agent. According to the invention, one or more drugs or therapeutic agents contained in microspheres are mixed with a temperature sensitive hydrogel which is then introduced directly to the desired situs of the drug or therapeutic agent. The temperature sensitive hydrogel may also contain a drug or a therapeutic agent, for example, a pain relieving drug, for a short-term controlled release. The temperature sensitive hydrogel is in liquid state at room temperature, but upon injection, shortly becomes gelatinous. This system is particularly suitable for treatment of diseases, disorders, or conditions, for example, tumors, discogenic back pain, or arthritis, warranting localized administration of a drug or a therapeutic agent. In addition, the specification provides a method for production of a drug- or therapeutic agent-containing microspheres.
