Composite microspheres induce the sustained release and the control of the initial release of water soluble drugs.

Although epidural analgesia may provide adequate pain relief and minimize systemic side effects, long-term, even permanent placement of epidural catheter for chronic or cancer-related pain management carries a potential risk of both superficial and deep infection. The development of antibiotics microspheres that could be dwelled in epidural drug-delivery devices is likely to achieve a significant advance allowing antibiotics given by the intradiscal route to control catheter-related infections. In the present study, the composite microspheres composed of double-walled microcapsules and PLGA were constructed for encapsulating water-soluble antibiotics, cefazolin. The results show that these microspheres could efficiently control the initial release of drug, which was only 3.0% at 2 h. Cefazolin encapsulated in the composite microspheres released gradually nearly in a constant rate in the first 16 days, and still maintained a relative fast rate in the next 14 days, indicating that composite microspheres could improve the incomplete release of entrapped drugs.