Abstract: Systems and methods for processing data relating to use of a drug by a patient that receive patient information and determine a dosage of the drug on the basis of the patient information. The systems and methods may be operated to provide patient-specific information on drug cost and on comparative costs of alternative drugs, on side effects, on allergies, and on pharmacology, as well as information on use in pregnancy, on use in lactation, on drug interactions, on warnings and contraindications, and supporting references. The systems may also be operated to prepare drug orders and prescriptions.