A method and apparatus for controlling the compounding of pharmaceutical parenteral admixtures is disclosed. The apparatus preferably comprises a computer that contains a memory for storing instructions for operating the apparatus and for controlling compounders that prepare a prescription admixture, with the memory including data relating to a plurality of the pharmaceutical components that may be transferred to prepare the prescription admixture, and data concerning the operating characteristics of the compounders that the apparatus is adapted to control. The apparatus determines the order of admixing by general rules of admixing and by categorized compatibility groups of components, so that the number of rinses that must be done are minimized.