The present invention is an aqueous solution which contains two types ofmethyl celluloses, polyethylene glycol, polyvinylpyrrolidone, and citric acidor apharmaceutically acceptable salt thereof. The composition of the presentinventionmaintains a low viscosity around room temperature, but the composition issuddenlyincreased in the viscosity due to heat around the body temperature and hasthixotropyeven after gelation.