Currently, checking the use of unapproved pharmaceuticals is required. Similarly, checking the use of contraindicated drugs is also necessary. We used a system to check the contraindications for the combined use of drugs for pregnant women and patients with allergies prior to prescription. Recently, we established a management structure involving the combination of a mechanical check system and subsequent pharmacist con rmation of contraindications for clinical conditions. In this study, we assessed the usefulness of this system. For one year, 41,431 contraindications for patients were mechanically extracted, and 24,861 contraindications were manually identi ed by pharmacists. These checks led to 51 prescription inquiries by pharmacists to doctors and to the modification of 18 prescriptions. Assuming that all unchanged prescriptions may have caused adverse events, the cost reduction was estimated to be 4,713,830 yen from a medically economic perspective. The combination of comprehensive automatic checks by the mechanical system and subsequent manual con rmation by pharmacists is bene cial for the management of contraindications and is expected to reduce the costs from a medically economic perspective.