title: Sustained delivery of retinoic acid from microspheres of biodegradable polymer in PVR.
abstract: OBJECTIVE
  The aims were to obtain a controlled intravitreous release of retinoic acid (RA) by injecting drug loaded microspheres of biodegradable polymers and to study the potential use of this RA delivery system in a rabbit model of proliferative vitreoretinopathy (PVR).
  
  
  METHODS
  The release of RA in vitro from 15 mg of 50-50 poly(DL-lactide-co-glycolide) (PLGA) in 1 ml of water at room temperature was measured with a spectrophotometer. In a rabbit model of PVR, 11 eyes were injected with 5 mg of microspheres containing 22 micrograms of RA/mg of PLGA, and seven control eyes were injected with microspheres of the same polymer that did not contain RA. In a third group, six rabbits were injected with 5 mg (n = 3) and 10 mg (n = 3) of microspheres containing RA.
  
  
  RESULTS
  The initial concentration of RA was 20.8 micrograms/mg of PLGA. The release curve showed a fairly constant daily release of 7 micrograms/d for about 30 days. At 40 days, the release rate decreased to about 6 micrograms/d. After 40 days, 82.8% of the RA was released. Four of 11 treated rabbits (36%) and 7/7 (100%) controls showed tractional retinal detachment (TRD) (P < 0.01) after 2 months. Histopathologically, a mild, localized, foreign body reaction was observed.
  
  
  CONCLUSIONS
  The authors obtained a sustained release of RA from PLGA microspheres in vitro for 40 days. A single injection of RA-loaded microspheres in suspension in BSS was effective in reducing the incidence of TRD after 2 months in a rabbit model of PVR.
authors.affiliation: Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: G G
authors.initials: GG
authors.lastname: Giordano
authors.forename: M F
authors.initials: MF
authors.lastname: Refojo
authors.forename: M H
authors.initials: MH
authors.lastname: Arroyo
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D003692:Delayed-Action Preparations; D004195:Disease Models, Animal; D004337:Drug Carriers; D005128:Eye Diseases / Q000188:drug therapy / Q000473:pathology; D005260:Female; D019344:Lactic Acid; D008297:Male; D008863:Microspheres; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D011817:Rabbits; D012163:Retinal Detachment / Q000473:pathology / Q000517:prevention & control; D012164:Retinal Diseases / Q000188:drug therapy* / Q000473:pathology; D014212:Tretinoin / Q000008:administration & dosage* / Q000627:therapeutic use; D014822:Vitreous Body / Q000473:pathology
chemical_list: D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014212:Tretinoin