Improved ocular absorption kinetics of timolol maleate loaded into a bioadhesive niosomal delivery system

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 REVbio) containing 0.25% TM. Presently we establish and report the pharmacokinetic and pharmacodynamic superiority of the developed ocular formulation of TM. Aqueous humor concentration of TM in male albino rabbits, after instillation of one drop of TM solution (TMS) or TMREVbio was measured using the microdialysis method. Peak concentration of drug in aqueous humor from TMREVbio (12.46 mu g/ml achieved at 60 min) was almost 1.7 times that of the control drug solution (TMS, 0.25%; 7.2 mu g/ml). An important observation was that the high drug concentrations achieved upon TMREVbio administration were maintained for up to 2 h. AUC for TMREVbio formulation was 2.34 times that of the TMS. This study confirms a sustained and controlled effect of the developed formulation.