The defined daily dose, or DDD, of a drug is a statistical measure of the average daily consumption of that drug necessary to maintain effectiveness in adults. This measurement is a statistical average and is not calculated based on the particular characteristics and needs of individual patients. As such, defined daily dose is not used for the purpose of prescribing medications but is instead used as means of comparing the necessary doses of different drugs or of the same drug by different groups of people. It is also commonly used in clinical research studies so that different quantities of a given drug used in such a study can be understood in terms of the average daily dose.
Comparison is one of the most important purposes of the defined daily dose. Different medications, even those used for the same purposes, are often administered at drastically different doses. One medication may have the same effect as another, but only when a much higher dose is administered. A doctor or researcher who reads about a medication may not understand the significance of any dosage information if it is presented without context. The defined daily dose provides that context, so a doctor or researcher can understand the significance of dosage information in comparison to the defined daily dose.
Research on a larger scale can also benefit from the use of defined daily dose statistics. Defined daily dose statistics can be collected for certain regions or demographics and can, therefore, be compared to others. Regional differences may suggest that the doses of certain medications prescribed in some regions are too large or too small. They may also suggest that, because of environmental, genetic, or other reasons, people of certain regions or backgrounds require higher or lower doses than average. These research studies can provide important information about a range of different topics including drug control and genetic or environmental drug responses.
It is important to note that the defined daily dose of a drug is not used for the purpose of prescribing medications. Factors such as weight, other medical complications, and specific environmental concerns are not normally taken into consideration. Prescriptions are made based on these and a range of other specific factors and may be considerably higher or lower than the defined daily doses of the medications prescribed. Defined daily doses may, however, provide medical professionals with a standard dosage level to which they can compare their prescribed dosage. Significant differences could suggest potentially harmful calculation errors.