Reversible gelling system for ocular drug delivery

The present invention is directed to ophthalmic compositions, particularly those provided as buffered, aqueous solutions. The subject compositions are useful as moisturizing and lubricating eye drops and as delivery vehicles for ophthalmic drugs. The invention provides an ophthalmic aqueous composition for topical administration, comprising:(a) a block copolymer of propylene oxide and ethylene oxide in concentration sufficient to provide viscosity of less than about 25 centipoise at ambient temperature and viscosity of from about 25 to about 55 centipoise when applied topically to a patient;(b) hydroxypropyl methylcellulose in concentration sufficient to improve the durability of the gel formed by the block copolymer.The invention further provides a method for administering ophthalmic pharmaceuticals.