The defined daily dose per 100 bed-days as a unit of comparison and a parameter for studying antimicrobial drug use in a university hospital. A retrospective study of the effects of guidelines and audit on antimicrobial drug use.

Growing awareness of problems arising from over-use of antimicrobial agents has led to attempts to develop policies or guidelines for rational treatment. To follow the effects of guidelines, the percentage of patients receiving anti-microbial drug therapy, acquired from patient records, has been a frequently used parameter. In this paper the Defined Daily Dose (DDD) per 100 bed-days has been used instead. This parameter can be calculated by converting the number of units of antimicrobials, delivered to individual wards, to defined daily doses per bed-day. This parameter determines the probability of treating a patient with a particular drug, based on pooled data. The DDD per 100 bed-days has been used to follow changes in prescribing habits arising from the acceptance of and adherence to guidelines over a period of 5 years in a University Hospital.