Study On Lidocaine Sustained-release Microsphere

Lidocaine is a local anesthetic of amide type.On clinical,to keep plasma-drug concentration,low dosage must be given frequently.In this paper,in order to prolong the anesthetic action,minimize the side effects and decrease the frequency of administration,suitable sustained-release microspheres containing lidocaine were prepared using Polylactic-co-glycolic acid(PLGA)as carrier.The content of Lidocaine was monitored by Ultraviolet spectrophotometry. Lidocaine has the absorption maximum at the wave length of 263nm, For Lidocaine physiological saline solution. The standard curves of Lidocaine is linear over the range of 0.01mg/ml-0.45mg/ml,and the equation of standard curves is A=1.684C+0.0109 R=0.9998;The average recovery rate(n=9)is 98.86%,RSD is 0.25%;It is stable within 2 days and precision test of Lidocaine within-day RSD = 0.92%.In this paper, emulsification-solvent evaporation method was developed to prepare Lidocaine-MS with PLGA as carriers. First, to study the best preparation process of microsphere without Lidocaine single factor experiments was done using the shape of microspheres as evaluating criterias. The best process:with the concentration of Tween-80 of 3%(v/v), ultrasonic emulsification of 1min,the stirring time of 6h, the centrifugal separation of 20min,the microspheres were dried using freezing drying.The influence of formulation and manufacture was studied with particle's size, the drug loading percent, the drug entrapment efficiency and the yield as evaluating criterias. The optimal formulation was verified by orthogonal design L₉(3³),based on the results of single factor experiments, The best prescription is: Lidocaine:PLGA= 1:5(w/w),the concentration of PLGA = 25%(g/ml),O:W=1:4(v/v).The characteristics of Lidocaine-MS prepared with optimal formulation were investigated and evaluated. The average diameter is 2.56,the drug loading percent is 8.89%, the entrapment is 53.34%,and the yield is 64.56%.By the study of drug release in vitro,it showed that the Lidocaine microspheres can release 48 hours. The release kinetics of lidocaine from PLGA-MS in vitro can be described by Higuchi equation.