PLGA-based microspheres containing ropivacaine and betamethasone for sciatic nerve block in mice

The aim of the present study was to develop Poly (lactic-co-glycolic acid) (PLGA)-based microspheres containing ropivacaine and betamethasone (RPC/BTM PLGA MS) by emulsion-solvent evaporation method. RPC/BTM PLGA MS were characterized by physical properties, such as morphology and particle size, and in vitro drug release. In addition, in vivo pharmacokinetics and pharmacodynamics of RPC/BTM PLGA MS were also investigated. The prepared RPC/BTM PLGA MS was suitable for local injection with a well-dispersed spherical shape, high stability, and high encapsulation efficiency. The mean diameter was 14.8 ± 1.2 µm and the polydispersity index (PDI) was 0.32 ± 0.04. In an in vitro study of drug release, it can be concluded that the RPC/BTM PLGA MS exhibited sustained and long-term release properties for 16 days. Furthermore, the result of an in vivo study indicated that the RPC/BTM PLGA MS had sustained release effect and the pharmacodynamics result showed that preparing RPC/BTM PLGA MS as microsphere preparation could not only extend the drug effect time but also prolong the duration of local anesthetics compared with the common RPC PLGA MS.