Abstract: The present invention provides a pharmaceutical formulation having thermoreversible properties, comprising: a) an anti-microbial agent; b) a poloxamer mixture containing at least two poloxamer polymers; and c) a hydroxy fatty acid ester of polyethylene glycol, wherein the formulation is a solid at room temperature and is a liquid-gel at body temperature. The thermoreversible pharmaceutical formulation has a viscosity of about 8,500 cP to about 400,000 cP at room temperature, and a viscosity of about 1,000 cP to about 8,000 cP at body temperature and exhibits a hysteresis loop behavior. The present invention further provides a process of preparing as well as a method of treating a microbial infection in a mammal using the same.