This study examined the impact of pharmaceutical inquiries regarding prescriptions on drug costs by surveying the actual condition of inquiries at 13 pharmacies. The study also investigated the significance of inquiries from a medical economics perspective by calculating the medical cost savings realized by preventing adverse drug reactions (ADRs). As a result, the total change in drug costs for the 13 pharmacies after pharmaceutical inquiries represented an increase of ¥9,018/month. However, upon recalculating the cost of drugs by assuming that those with an "Incomplete entry in the prescription (compared with previous prescription, etc.)" should in fact have been prescribed, and excluding them, the total drug costs for the 13 pharmacies is decreased to ¥154,743/month, translating to a cost-savings of ¥7.2/prescription. The study then undertook a comprehensive assessment based on the Diagnosis Procedure Combination (DPC) system to determine the total medical cost-savings for 5 patients in whom ADRs could have occurred if the prescriptions had not been modified as a result of pharmaceutical inquiries. The obtained figure of ¥1,188,830 suggests that pharmaceutical inquiries contribute to reduced medical costs. The findings of this study indicate that pharmaceutical inquiries regarding prescriptions by staff pharmacists not only ensure the proper delivery of drug therapy to patients, but are also effective from a medical economics perspective.