Guidelines for ATC classification and DDD assignment - WHOCC

The WHO Collaborating Centre for International Drug Monitoring (Uppsala
Monitoring Centre), Sweden, receives spontaneous reports of suspected adverse
reactions from national centres (96 countries are included in the programme,
October 2009). Information on all medicinal products appearing in these reports is
stored in a drug register, linked to the reports database. All single and multiple
ingredient preparations are given an ATC code at the substance level, which allows
flexible searches comprising different drug categories or groups of drugs. The
ATC system is also used for the grouping of drugs in output documents.
D. "Double medication" and "pseudo-double medication"
The ATC classification can be used as a tool for screening of "double"- and
"pseudo-double medication".
“Double medication" can be defined as using two identical drugs simultaneously
(e.g. two different diazepam preparations) whereas "pseudo-double medication"
can be defined as using two chemically different substances but with similar
pharmacodynamic properties simultaneously (e.g. a diazepam preparation plus an
oxazepam preparation).
The objective of checking these situations, by using physician or pharmacy patient
computer records, is to prevent unnecessary medication, which may increase the
risk of side effects.
In the case of plain preparations, the ATC 5th level codes can be used; while the
level to which monitoring must be made depends on the ATC group concerned.
For combination products the ATC 5th level code is not always sufficient to
identify all active ingredients. It is therefore recommended to connect all ATC
codes given for each of the different active ingredients to each combined
preparation.
E. Drug catalogues
ATC codes are included in some international drug catalogues (e.g. the Martindale)
and in several national drug catalogues.
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