In situ gel can be defined as a polymer solution administered as a liquid and when exposed to some physiologic condition such as thepH, ionic, temperature modulation or solvent and UV induced gelation undergo to phase transition to a semisolid gel. Ketotifenfumarate belongs to the histamine H1 receptor antagonists, and Ketotifen fumarate is used in the treatment of allergic conditions likeconjunctivitis and rhinitis. This work aims to study the natural polymer effects (xanthan gum,gellan gum) on the properties of pH-trigger in situ ocular gel, then compared the drug-releasing rate of optimized formula with the market ketotifen eye drop. Eightformulations (F1-F8) were prepared using different concentrations of xanthan gum, gellan gum with carpbapol based gel. The bestformulation F5 prepared by using0.75% carbapol940 as a gelling agent with 0.3% xanthan gum as a viscosity builder and 0.02% methylhydroxyl benzoate as a preservative with drug content 99.74%±1.31, pH value, 5.2±0.31, Gel strength 46.6±0.1sec with sustaineddrug release over period 8h
