Methods to form an active agent modified monomer comprising a ring opening cyclic monomer linked to an active agent via a degradable covalent linkage. Methods to form a polymer or copolymer comprising an active agent modified monomer. Methods to form an active agent modified monomer comprising combining a ring opening cyclic monomer with a first functional group (X) and an active agent with a second functional group (Y) to form an active agent modified monomer, wherein the first (X) and second (Y) functional groups are complementary functional groups that form a degradable linkage. The active agent modified monomer can also comprise a non-degradable linkage. The method can form a ring opening cyclic monomer that includes a cyclic carbonate, cyclic epoxide, lactam, lactone, lactide anhydride, cyclic carbamate, cyclic phosphoester, or siloxane. Apparatus that includes a medical device that comprises a polymer or copolymer that comprises an active agent modified monomer.