The crucial question of standardisation when measuring drug consumption.

The reliability of drug consumption studies will depend on agreement on an international unit of measurement and the provision of accurate descriptions of patterns of use. This measurement unit should permit comparisons between countries and periods of time. Different units have been proposed and published. Consumption may be expressed in terms of pharmaceutical firm turnover, therapeutic costs, weight (total weight or dose equivalent), treatment doses such as defined daily dose and prescribed daily dose, or as number of items or packages sold. The advantages and disadvantages of the different evaluation units used in veterinary medicine are reviewed.