Between September and November 1993, 15 people died due to the interaction between sorivudine (anti-virus drug: commercial name is Usevir) and fluorouracil analogs (anti-tumor drug). Questionnaires were completed by the physicians who had opportunities of prescribing fluorouracil analogs as part of post-marketing randomized clinical trials at that time. Two types of questionnaires were designed. One questionnaire was regarding the doctor's general recognition of interactions among drugs. The other questionnaire asked doctors about their specific action concerning individual patients. Questionnaires were collected from 270 doctors covering about 610 patients; 87.8% of the doctors had already been informed of the interaction between sorivudine and fluorouracil analogs. Newspapers (48.5%) were the largest source of information. Only 2.5% of the doctors acquired their information from the package insert with the drugs. Of the doctors questioned, 51.2% had the possibility to administrate the drug even though “combination should be avoided” was printed on the drug package insert. The 2nd questionnaire about the actions of the doctors showed that in 44.8% cases doctors checked whether sorivudine was used in any way and in 47.7% of cases doctors did not check at all.
There are several points regarding the tragedy of sorivudine. The factors related to this tragedy include the system to check the interaction between drugs, telling patients the truth about cancer, and patient consultation regarding medication. These problems originate from the Japanese system of tansmission of drug information. The results of the present survey indicate that it is very difficult to detect drug interaction, to transmit this information to doctors and to inform patients in today's Japanese system. The possibility of a second sorivudine tragedy cannot be denied.