DDD

1. DDD – Defined Daily Dose

2. Definition Defined Daily Dose (DDD): The assumed average maintenance dose per day for a drug used for its main indication in adults.

3. DDD.. By applying DDD it is possible to: • Examine changes in drug utilization over time • Make international comparisons • Evaluate the effect of an intervention on drug use • Document the relative therapy intensity with various groups of drugs • Follow the changes in the use of a class of drugs • Evaluate regulatory effects and effects of interventions on prescribing patterns.

4. DDD Indicators DDD per 1000 inhabitants per day The figure 10 DDDs per 1000 inhabitants per day can be interpreted as follows: in a representative group of 1000 inhabitants, 10 DDDs of the drug are utilized on average, on any given day of the year analysed. Alternatively this can be expressed as 10/1000 (1%) of the population are receiving this drug each day in that year. This estimate is most useful for drugs used chronically and when there is good agreement between the average prescribed daily dose (PDD) and the DDD.

5. DDD Indicators DDD per 100 bed days: A bed day is a day during which a person is confined to a bed and in which the patient stays overnight in a hospital. The figure 70 DDDs per 100 bed days of hypnotics provides an estimate of the therapeutic intensity and estimates that 70% of the inpatients receive one DDD of a hypnotic every day. This measure is applied in analyses of in-hospital drug use. This indicator is quite useful for benchmarking in and between hospitals.

6. DDD Indicators Expenditure per DDD This indicator represents the actual cost paid by a health system for specific medicines. This indicator provides information on the actual cost paid for a medicine and allows comparison between countries (international differences in the expenditure for the same medicine). It also allows comparison between medicines licensed with comparable clinical properties and allows the calculation of exact differences within a country or between countries. This indicator must be interpreted with caution if the indications for use differ and if the ratio between the DDD and the prescribed daily dosage differ significantly within a drug group.

7. DDD Indicators DDD/patient: This indicator is often calculated in pharmacoepidemiological databases and expresses the treatment intensity/total exposure according to a defined study period. If the actual dose used is equivalent to the DDD, the DDD/patient would also express the number of treatment days in a specific period. Drug utilization data presented in DDDs give a rough estimate of consumption and not an exact picture of the actual drug use, and the estimates described above are only true if there is good agreement between the actually prescribed dose and the DDD.

8. DDD Indicators With access to drug utilization statistics based on the ATC/DDD system, it is possible to construct simple indicators reflecting the quality of prescribing or drug use. The adherence to prescribing guidelines can be assessed using the percentage of use of the recommended drug of the total use of drugs in a certain group The recommended drugs, as well as the drug group, can be defined using ATC codes. 

9. ATC • Anatomical Therapeutic Chemical (ATC) classification system, the active substances are divided into different groups according to the organ or system on which they act and their therapeutic, pharmacological and chemical properties.

10. ATC/DDD DDDs are only assigned for medicines given an ATC codes The DDDs are allocated to drugs by the WHO Collaborating Centre in Oslo Only one DDD is assigned per ATC code and route of administration (e.g. oral formulation) DDDs are not established for all medicines with an ATC code. E.g. topical products.