The relationship between the number of combined drugs on prescriptions for outpatients and frequency of their interactions was studied. The investigation was made from Monday through Friday. The combination of 1 to 4 drugs accounted for 62.3%, including that of 3 drugs which composed the largest part of 17.3%. The average number of combined drugs was largest, 5.2, at the department of internal medicine. The interactions were observed in 3.8 % of the total prescriptions. They were caused by contraindications in 6.1%, inappropriate combinations in 8.2%, and caution for combination in 85.7%. The rate of interactions was highest, 44.9%, at the department of psychiatry, followed by 45.9% in 3 divisions of internal medicine.
Some cases of contraindications were thus noted in the study, but it was found that most of the doctors take precaution against interactions in prescribing. drugs for combination. In the future, information for doctors and instruction of patients in using drugs must be promoted on the basis of extensive investigation of interactions of drugs on prescriptions for inpatients and parenteral preparations.
