4.2 How are AMU and AMC measured?

AMU and AMC are also measured at different levels. Measuring AMU at a single site (such as a hospital or pharmacy) is useful for developing local prescribing guidelines and evaluating the impact of antimicrobial stewardship programs. AMU data at site level can also feed into surveillance systems that integrate data from multiple surveillance sites. There are many indicators that can be used to measure AMU at a single site. The Systems for Improved Access to Pharmaceuticals and Services (SIAPS) program, supported by USAID, describes four categories of indicators that could be used in hospitals to monitor AMU (Systems for Improved Access to Pharmaceuticals and Services (SIAPS) Program, 2012). Each of these categories, along with a few example indicators is shown in Table 7.

Quantifying the amount of antimicrobials that are taken by humans or animals is not always straightforward. At first it might seem simple – we could just count the number of tablets a patient takes, for example. But in fact there is a substantial amount of variation that makes it challenging to make AMU data comparable across different data units, settings and sectors. For example:

• There are multiple routes of administration, include oral, parenteral, rectal, intramuscular injections, and as part of medicated feed and water in terrestrial and aquatic animals.
• The concentration of active antimicrobial ingredient varies in different products and formulations (for example, tablet versus liquid forms).
• Patients and animals receive different amounts (doses) according to their age and bodyweight.
• A treatment course may be administered as a high dose in a single day, or a lower dose taken daily for several days.
• Informal/non-prescribed use, e.g. over-the-counter purchases.