A composition comprising: a plurality of microparticles, wherein substantially all of the plurality of microparticles comprise one or more local anesthetic compounds, wherein at least some of the plurality of microparticles comprise at least one polymer from which the local anesthetic compound is releasable, wherein at least some of the plurality of microparticles comprise one or more local anesthetic compounds in an amount of at least 70 % by weight, wherein the average amount of local anesthetic compound in the composition is at least 50 % by weight, and wherein the composition optionally further comprises a local anesthetic effect-augmentation agent which, if present, is included in the composition in an amount of less than 0.005 % by weight, characterized in that the plurality of microparticles comprises a mixture of at least two groups of microparticles, each group having an average polymer molecular weight, an average drug loading percentage, and an average particle size, wherein at least the average polymer molecular weight is different in each of the groups, wherein at least one of the local anesthetic compounds is chosen from the group consisting of: lidocaine, bupivacaine, ropivacaine, dibucaine, etidocaine, tetracaine, xylocaine, procaine, chloroprocaine, prilocaine, mepivacaine, mixtures thereof and salts thereof, and wherein the at least one polymer is chosen from the group consisting of polyesters, polyorthoesters, proteins, polysaccharides, and combinations thereof, poly(lactic) acid, poly(glycolic) acid, polyactide,polyglycolides, poly(DL-lactic-co-glycolic) acid, polyanhydride, polycaprolactone, and polyphosphazene. a plurality of microparticles, wherein substantially all of the plurality of microparticles comprise one or more local anesthetic compounds, wherein at least some of the plurality of microparticles comprise at least one polymer from which the local anesthetic compound is releasable, wherein at least some of the plurality of microparticles comprise one or more local anesthetic compounds in an amount of at least 70 % by weight, wherein the average amount of local anesthetic compound in the composition is at least 50 % by weight, and wherein the composition optionally further comprises a local anesthetic effect-augmentation agent which, if present, is included in the composition in an amount of less than 0.005 % by weight, characterized in that the plurality of microparticles comprises a mixture of at least two groups of microparticles, each group having an average polymer molecular weight, an average drug loading percentage, and an average particle size, wherein at least the average polymer molecular weight is different in each of the groups, wherein at least one of the local anesthetic compounds is chosen from the group consisting of: lidocaine, bupivacaine, ropivacaine, dibucaine, etidocaine, tetracaine, xylocaine, procaine, chloroprocaine, prilocaine, mepivacaine, mixtures thereof and salts thereof, and wherein the at least one polymer is chosen from the group consisting of polyesters, polyorthoesters, proteins, polysaccharides, and combinations thereof, poly(lactic) acid, poly(glycolic) acid, polyactide,polyglycolides, poly(DL-lactic-co-glycolic) acid, polyanhydride, polycaprolactone, and polyphosphazene.