title: Improved ocular absorption kinetics of timolol maleate loaded into a bioadhesive niosomal delivery system.
abstract: BACKGROUND
  Application of timolol maleate (TM) in a conventional dosage form (solution) into the eye results in almost 80% of the instilled dose being lost either through spillage or due to drainage into the nasolacrimal duct. Later results in systemic side-effects especially in patients suffering from heart diseases or bronchial asthma thus limiting the usefulness of TM for the control of glaucoma. Earlier we had reported on the development of a mucoadhesive coated niosomal system for TM (TM REV(bio)) containing 0.25% TM. Presently we establish and report the pharmacokinetic and pharmacodynamic superiority of the developed ocular formulation of TM.
  
  
  METHODS
  Aqueous humor concentration of TM in male albino rabbits, after instillation of one drop of TM solution (TMS) or TMREV(bio) was measured using the microdialysis method.
  
  
  RESULTS
  Peak concentration of drug in aqueous humor from TMREV(bio) (12.46 microg/ml achieved at 60 min) was almost 1.7 times that of the control drug solution (TMS, 0.25%; 7.2 microg/ml). An important observation was that the high drug concentrations achieved upon TMREV(bio) administration were maintained for up to 2 h. AUC for TMREV(bio) formulation was 2.34 times that of the TMS.
  
  
  CONCLUSIONS
  This study confirms a sustained and controlled effect of the developed formulation.
authors.affiliation: University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh, 160014, India. indupalkaur@yahoo.com
authors.forename: Indu Pal
authors.initials: IP
authors.lastname: Kaur
authors.forename: Deepika
authors.initials: D
authors.lastname: Aggarwal
authors.forename: Harinder
authors.initials: H
authors.lastname: Singh
authors.forename: Shilpa
authors.initials: S
authors.lastname: Kakkar
mesh_terms: D000042:Absorption; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003315:Cornea / Q000378:metabolism*; D016503:Drug Delivery Systems; D007429:Intraocular Pressure / Q000187:drug effects; D008081:Liposomes; D008297:Male; D017551:Microdialysis; D010539:Permeability; D011817:Rabbits; D013999:Timolol / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D000319:Adrenergic beta-Antagonists; D008081:Liposomes; D013999:Timolol