The use of a computer-based consultation program to customize dosage regimens of antimicrobials for patients with meningitis or bacteremia is described. Using clinical and laboratory information entered by the user, the program determines causative organisms, recommends therapeutic regimens, and generates a graph depicting the expected blood level of each drug as a function of time. During therapy selection, the program considers the site of infection, the susceptibility of the organism to antibiotics, and the patient's clinical status and drug history. Individualized pharmacokinetic values allow for dosage adjustments in renal failure and estimation of blood levels. If renal impairment is present, dosage regimens for drugs excreted by the kidneys are adjusted to assure the desired steady-state blood levels. To help in selection of the optimal regimen, estimated blood levels for each regimen are graphed along with the minimum inhibitory concentration for the organism and the toxic level of the drug. A bulit-in knowledge base in conjunction with patient-specific information enables the computer program to determine appropriate treatment specific to a patient's age, renal function, and prior drug reactions.