Average daily quantities: a tool for measuring prescribing volume in England.

No perfect unit exists for measuring prescribing volume, because of the limitations of the prescription item and the Defined Daily Dose system. A specific English and easily understandable unit was thought desirable to allow discussions in the field with doctors about aspects of their prescribing. An expert group was therefore established to produce appropriate volume units (Average Daily Quantities, ADQs) for important drug groups, based on DDDs, average prescribed daily doses, and any available information on therapeutic equivalence. This system will be a useful tool for discussions with doctors concerning their prescribing. It is of some value for researchers performing drug utilization studies and studies on prescribing in England. The ADQ values will be reviewed regularly to ensure that changes in licensed doses, actual prescribing patterns, and DDDs are reflected, and that new drugs can be included. Copyright (c) 2000 John Wiley & Sons, Ltd.