Abstract: A method of preserving formulations is provided. The method includes the step of including a derivatized cyclodextrin in a formulation capable of sustaining microbial growth. One embodiment of the formulation employs a sulfoalkyl ether cyclodextrin as a preservative and optionally as a solubilizing and complexing agent. A suitable cyclodextrin is the CAPTISOL” brand cyclodextrin (sulfobutyl ether R-cyclodextrin). Whether or not the formulation includes a conventional preservative, the formulation will remain preserved for at least a minimum predetermined period. Specific embodiments of the invention include a carrier, a derivatized cyclodextrin and optionally one or more active agents, one or more water activity-reducing agents, and/or one or more complexation-enhancing agents. The derivatized cyclodextrin reduces the water activity of the formulation. A liquid formulation can be lyophilized or otherwise dried to yield a solid formulation that is optionally reconstitutable.