Computer systems and non-transitory computer readable media for determining an amount of an ingredient for a preparation for a requested therapy (e.g., an order or a prescription) includes an identifier, volume, and amounts of first and second compounds in each of a plurality of premix solutions. A predefined formulary comprising a formulary concentration of each of a plurality of additions is provided. A premix solution is selected. An amount of a first additions to be added to the premix solution may be selected. A number of bags of the premix solution, needed to satisfy a volume associated with the selected premix solution, are optionally reserved. An additive volume is determined at least by the specified first amounts of the first addition and a corresponding formulary concentration.