Formulation and in vitro-in vivo evaluations of timolol maleate viscous eye drops for the treatment of glaucoma

The purpose of this research was to provide comfort and compliance to the patient and yet improve the therapeutic performance of the drug over conventional systems by preparing of functional and patient friendly viscous eye drops of Timolol Malate (TM) for the treatment of glaucoma. Hydroxy propyl methyl cellulose (HPMC K4M) and Carbopol 940 (CP 940) were explored as potential viscosity enhancing vehicles for prolonging the therapeutic effectiveness. The developed viscous eye drops were evaluated for clarity, pH, osmolarity, viscosity, mucoadhasion test and in vitro drug release. The optimized formula was subjected for in vivo testing by measurement of IOP (intraocular pressure), ocular irritation test and stability studies. TM viscous eye drops containing 1 % HPMC K4M and 0.3 % CP 940 exhibited non-newtonian flow behavior. HPMC K4M and CP 940 were responsible for higher viscosity and mucoadhasion respectively. Developed viscous eye drops exhibited the diffusion mechanism of drug release. The values of slope (n) were in the range of 0.65 to 0.99. IOP measurement of rabbit eye treated with optimized batch showed significant reduction in ocular pressure for 8 hrs. Ocular irritation test in rabbits showed no redness, swelling or watering. The overall study reveals that ratio of HPMC K4M (0.75 mg) and CP 940(0.075 mg) was gave favorable clinical response and used to prolong the therapeutic effectiveness of TM.