title: Poly(ortho ester) biodegradable polymer systems.
mesh_terms: D000812:Anhydrides; D001673:Biodegradation, Environmental; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage; D003692:Delayed-Action Preparations; D004355:Drug Stability; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D016912:Levonorgestrel; D008722:Methods; D009640:Norethindrone / Q000008:administration & dosage; D009644:Norgestrel / Q000008:administration & dosage; D011091:Polyesters / Q000138:chemical synthesis; D012995:Solubility
chemical_list: D000812:Anhydrides; D003277:Contraceptives, Oral, Combined; D003692:Delayed-Action Preparations; D011091:Polyesters; D009644:Norgestrel; D016912:Levonorgestrel; D009640:Norethindrone