The invention relates to a device for use in the clinical/therapeutical field for the patient-individual optimization of the dosage and/or the dosage scheme of a drug based on rational, mathematical models which take into consideration possible physiological variations that are due to the illness or other particularities of the patient and the interaction with co-drugs that are administered at times close to each other. The invention also relates to the supply of said drug dose by means of a dosage device.