Abstract: Decision information systems, methods, and computer programs for better informing decisions to use multiple drugs in drug delivery devices, including implantable devices, for drug administration. Executable computer programs and logic embodying methods of the invention can calculate consistent multiple drug mixture amounts and drug delivery flow rates. One program accepts user input indicating a desired first drug dose rate, an initial first drug concentration, a desired second drug dose rate, an initial second drug concentration, and the reservoir size of the drug delivery device. The program method calculates a first drug amount and a second drug amount to combine in a mixture as well as a first drug true concentration in the mixture. The drugs can be mixed consistent with the physician's instructions using the program output. The first drug true concentration can be entered into a programmer device as the only drug concentration entered.