A delivery system, comprising: a liquid polyorthoester; a dipolar aprotic solvent that is selected from dimethyl sulfoxide, dimethyl acetamide and N-methyl pyrrolidone in which the polyorthoester is miscible to form a single phase; and between 1-20 wt% of an amino amide anesthetic dispersed or solubilized in the single phase; wherein the amino amide anesthetic is released from the system at a rate effective for reducing or preventing pain; and wherein the system comprises between 50-80 wt% of polyorthoester represented by the structure shown as Formula III: where: R* is a C 1-4 alkyl; n is an integer of at least 5; and A is R 1, R 2, R 3, or R 4, where R 1 is: where: p and q are integers that vary from between about 1 to 20 and the average number of p or the average of the sum of p and q is between 1 and 7 in at least a portion of the monomeric units of the polymer; R 5 is hydrogen or C 1-4 alkyl; and R 6 is: where: s is an integer of 0 to 30; t is an integer of 2 to 200; and R 7 is hydrogen or C 1-4 alkyl; R 2 is: R 3 is: where: x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and R 4 is the residue of a diol containing at least one functional group independently selected from amide, imide, urea, and urethane groups. a liquid polyorthoester; a dipolar aprotic solvent that is selected from dimethyl sulfoxide, dimethyl acetamide and N-methyl pyrrolidone in which the polyorthoester is miscible to form a single phase; and between 1-20 wt% of an amino amide anesthetic dispersed or solubilized in the single phase; wherein the amino amide anesthetic is released from the system at a rate effective for reducing or preventing pain; and wherein the system comprises between 50-80 wt% of polyorthoester represented by the structure shown as Formula III: where: R* is a C 1-4 alkyl; n is an integer of at least 5; and A is R 1, R 2, R 3, or R 4, where R 1 is: where: p and q are integers that vary from between about 1 to 20 and the average number of p or the average of the sum of p and q is between 1 and 7 in at least a portion of the monomeric units of the polymer; R 5 is hydrogen or C 1-4 alkyl; and R 6 is: where: s is an integer of 0 to 30; t is an integer of 2 to 200; and R 7 is hydrogen or C 1-4 alkyl; R 2 is: R 3 is: where: x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and R* is a C 1-4 alkyl; n is an integer of at least 5; and A is R 1, R 2, R 3, or R 4, where R 1 is: where: p and q are integers that vary from between about 1 to 20 and the average number of p or the average of the sum of p and q is between 1 and 7 in at least a portion of the monomeric units of the polymer; R 5 is hydrogen or C 1-4 alkyl; and R 6 is: where: s is an integer of 0 to 30; t is an integer of 2 to 200; and R 7 is hydrogen or C 1-4 alkyl; R 2 is: R 3 is: where: x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and p and q are integers that vary from between about 1 to 20 and the average number of p or the average of the sum of p and q is between 1 and 7 in at least a portion of the monomeric units of the polymer; R 5 is hydrogen or C 1-4 alkyl; and R 6 is: where: s is an integer of 0 to 30; t is an integer of 2 to 200; and R 7 is hydrogen or C 1-4 alkyl; R 2 is: R 3 is: where: x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and s is an integer of 0 to 30; t is an integer of 2 to 200; and R 7 is hydrogen or C 1-4 alkyl; R 2 is: R 3 is: where: x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and x is an integer of 0 to 100; y is an integer of 2 to 200; R 8 is hydrogen or C 1-4 alkyl; R 9 and R 10 are independently C 1-12 alkylene; R 11 is hydrogen or C 1-6 alkyl and R 12 is C 1-6 alkyl; or R 11 and R 12 together are C 3-10 alkylene; and