title: Gamma irradiation effects on stability of poly(lactide-co-glycolide) microspheres containing clonazepam.
abstract: This work was aimed at evaluating the effects of gamma irradiation on the stability of microspheres made of a poly(lactide-co-glycolide) copolymer (PLGA) and loaded with 15% w/w of clonazepam (CLO). The influence of CLO on PLGA radiolysis mechanisms and the identification of possible irradiation markers were also investigated. Microspheres were prepared by means of a spray-drying method. gamma Irradiation was carried out either under vacuum or in air, at a dose of 25 kGy, by using a 60Co source. The stability of CLO loaded microspheres was evaluated over a 6-month period on the basis of drug content and dissolution profile. Radiolysis mechanisms were investigated by using electronic paramagnetic resonance (EPR) analysis. The microspheres irradiated under vacuum were stable over the considered period of time. After irradiation in air, CLO release rate increased by approximately 10%, and did not change further in the following period of storage. The EPR analysis showed some radicals arising from both the polymeric matrix and the active ingredient. Polymer/CLO spin transfer reactions suggest that CLO had a radio-stabilising effect on the polymeric matrix. In the loaded microspheres, the intensity in time of the CLO radical signal is sufficient for its possible use as irradiation marker.
authors.affiliation: Istituto di Chimica Farmaceutica e Tossicologica, Università di Milano, v. le Abruzzi 42, 20131, Milan, Italy. luisa.montanari@unimi.it
authors.forename: L
authors.initials: L
authors.lastname: Montanari
authors.forename: F
authors.initials: F
authors.lastname: Cilurzo
authors.forename: L
authors.initials: L
authors.lastname: Valvo
authors.forename: A
authors.initials: A
authors.lastname: Faucitano
authors.forename: A
authors.initials: A
authors.lastname: Buttafava
authors.forename: A
authors.initials: A
authors.lastname: Groppo
authors.forename: I
authors.initials: I
authors.lastname: Genta
authors.forename: B
authors.initials: B
authors.lastname: Conti
mesh_terms: D002152:Calorimetry, Differential Scanning; D002998:Clonazepam / Q000008:administration & dosage* / Q000737:chemistry / Q000528:radiation effects; D004355:Drug Stability; D004578:Electron Spin Resonance Spectroscopy; D005720:Gamma Rays; D019344:Lactic Acid / Q000008:administration & dosage*; D008863:Microspheres; D011100:Polyglycolic Acid / Q000008:administration & dosage*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000008:administration & dosage*; D012995:Solubility
chemical_list: D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D002998:Clonazepam