Analysis of Contraindicated Combinations Using a Check System tor Drug Interactions, Including those of Injections-Pharmacists Should Verify Drug Interactions in Patient Medication Histories

In order to avoid adverse drug-interactions, we improved a computerized check system incorporated in the physician order-entry system. The improved system checks all drugs prescribed for a patient, including injections, and does not allow contraindicated combinations of drugs to be used. Our system also has a function for recommending safer substitutions for contraindicated drugs. In cases where contraindicated combinations are unavoidable, physicians may prescribe them by entering a password that is valid for one day only. The improved system can also evaluate the kinds of contraindicated combinations that physicians intend to prescribe. On checking our system's database, we found that there had been 299 contraindication alerts during 13 months for 589, 973 prescriptions. Also, the incidence of attempts to prescribe contraindicated drugs after clinical hours was almost 4 times as high as that during clinical hours. The contraindicated drug combinations were found in more than one type of prescription. Surprisingly, 80% of contraindicated combination events involved in injections and more than a half of contraindicated combinations were oral medicines with injections. We released alerts when requested by physicians when we judged these requests to be reasonable and 77 alerts were released during the 13-month period.Thus, our computerized system, which checks drugs as physicians enter orders for them, should be extremely useful in ensuring medication safety. Our findings indicate the possibility that pharmacists are often unaware of the contraindicated combinations after physicians have ordered prescriptions, and also the desirability of pharmacists verifying drug interactions in patient medication histories.