The DDD value in grams of every drug is defined by the WHO and is periodically updated. DDD values of every antibiotic are calculated separately.
Defined Daily Doses (DDDs) are calculated separately for every antibiotic, the average maintenance dose for an adult weighing 70 kg is prepared in main indications and the active substance should be taken as grams (or I.U.).
DDDs = Number of boxes x number of tablets in the box or number of vials x tablets in grams or the weigh of the vial / the DDD value of the antibiotic in grams.
In this calculation method, the form used for in-bed patients is the ratio of the total DDD per 100-bed-days. This index is called antimicrobial consumption index (ACI)
ACI = DDD=bed−days X 100
Also, the antibiotic consumption index of a country or geographical area at a certain period of time is calculated by DDD per 1000 people.
The number obtained is the antibiotic consumption index of that hospital/clinic or population.