What are the alternatives to DDD?
One of the more commonly used alternatives to DDDs is the Days of Therapy (DOT).
One DOT represents the administration of a single antibiotic on a given day regardless of the number of doses administered or dosage strength. For example, administration of cefuroxime as a single 1.5g dose or as three 750mg doses eight hours apart would both represent 1.0 DOT.
The use of DOT may overcome some of the disadvantages of DDDs. They can be used in paediatrics and they are not influenced by differences in dose recommendations/prescribed doses. However, they do not resolve the issue of the incentive to use a single broad-spectrum antibiotic where combinations of two or more narrow spectrum antibiotics will contribute more DOT than a single broad-spectrum agent. Perhaps their main disadvantage is they are time consuming and relatively more difficult to measure as they require patient level information.
Other ways of expressing antibiotic use are:
Cost - These data are easy to obtain and are generally easily understood by administrators but price differences between different products and changes over time limit their usefulness as a metric.
Volume - Common physical units such as grams are easy to obtain and can be used to produce DDD.
Prescribed Daily Dose - The Prescribed Daily Dose (PDD) can be determined from prescription studies, medical or pharmacy records and patient interviews. It is important to relate the PDD to the infection for which the antibiotic is required. There can be differences in the PDD between countries based on national treatment guidelines.
So despite the inherent disadvantages, the DDD has become established as a universal, standardised metric for the surveillance of antibiotic use.
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