Objective: To investigate the pharmacokinetics and pharmacodynamics of poly (lactide-co-glycolide) microspheres containing ropivacaine and dexamethasone for sciatic nerve block in mice.
Methods: A total of 165 female mice were randomly assigned into 3 groups, namely dexamethasone-loaded ropivacaine microsphere group (group A, n=55), ropivacaine microsphere group (group B, n=55) and PLGA microsphere group (group C, n=55). The mice received surgical implantation of the corresponding preparations near the sciatic nerve at the dose of 400 mg/kg. Hot plate test was used to evaluate the anesthetic effect of these microspheres at different time points after the implantation, and high-performance liquid chromatography (HPLC) was employed to determine plasma ropivacaine concentration.
Results: Pharmacodynamic study showed that the duration of sciatic nerve sensory block was significantly longer in group A than in group B (P<0.05). The analysis of pharmacokinetics variables demonstrated that T(1/2) in group A was prolonged as compared with that of group B. No anesthetic effect was observed in group C.
Conclusion: Dexamethasone-loaded ropivacaine microspheres can significantly prolong the analgesic effect of ropivacaine in mice.