title: Sustained ocular drug delivery from a temperature and pH triggered novel in situ gel system.
abstract: Various ocular diseases like glaucoma, conjunctivitis, and dry eye syndrome require frequent drug administration. Poor ocular bioavailability of drugs (< 1%) from conventional eye drops is due mainly to the precorneal loss factors that include rapid tear turnover, nonproductive absorption, transient residence time in the cul-de-sac, and the relative impermeability of the drugs to corneal epithelial membrane. These problems may be overcome by the use of in situ gel-forming systems that are instilled as drops into the eye and undergo a sol-gel transition in the cul-de-sac. Our present work describes the formulation and evaluation of an ocular delivery system of timolol maleate based on the concept of both temperature and pH-triggered in situ gelation. Pluronic F-127 (a thermosensitive polymer) in combination with chitosan (pH-sensitive polymer also acts as permeation enhancer) was used as gelling agent. The developed formulation was characterized for various in vitro parameters e.g., clarity, gelation temperature and pH, isotonicity, sterility, rheological behavior, drug release profile, transcorneal permeation profile, and ocular irritation. Developed formulation was clear, isotonic solution, that converted into gel at temperatures above 35 degrees C and pH 6.9-7.0. A significant higher drug transport across corneal membrane and increased ocular retention time was observed using the developed formulation. The developed system is a viable alternative to conventional eye drops for the treatment of glaucoma and various other ocular diseases.
authors.affiliation: Division of Cyclotron and Radiopharmaceutical Sciences, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization, Timarpur, Delhi, India.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Gupta
authors.forename: Sanyog
authors.initials: S
authors.lastname: Jain
authors.forename: Rashi
authors.initials: R
authors.lastname: Mathur
authors.forename: Pushpa
authors.initials: P
authors.lastname: Mishra
authors.forename: Anil K
authors.initials: AK
authors.lastname: Mishra
authors.forename: T
authors.initials: T
authors.lastname: Velpandian
mesh_terms: D000818:Animals; D001682:Biological Availability; D002642:Chick Embryo; D048271:Chitosan / Q000737:chemistry; D049033:Chorioallantoic Membrane / Q000187:drug effects; D003315:Cornea / Q000378:metabolism; D003692:Delayed-Action Preparations / Q000737:chemistry; D016503:Drug Delivery Systems / Q000379:methods*; D004349:Drug Packaging / Q000379:methods; D005128:Eye Diseases / Q000188:drug therapy*; D005260:Female; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry*; D006041:Goats; D006863:Hydrogen-Ion Concentration; D007322:Instillation, Drug; D008297:Male; D010226:Parabens / Q000737:chemistry; D020442:Poloxamer / Q000737:chemistry; D011817:Rabbits; D011877:Radionuclide Imaging; D013696:Temperature; D013999:Timolol / Q000008:administration & dosage* / Q000493:pharmacokinetics; D023382:Toxicity Tests, Acute; D014783:Viscosity
chemical_list: D003692:Delayed-Action Preparations; D005782:Gels; D010226:Parabens; D020442:Poloxamer; D013999:Timolol; D048271:Chitosan; C015358:methylparaben