Guidelines for ATC classification and DDD assignment ... - WHOCC

Preference will be given to establishing a new pharmacological 4th level rather thana chemical subgroup.Substances classified in the same ATC 4th level cannot be consideredpharmacotherapeutically equivalent since their mode of actions, therapeutic effects,drug interactions and adverse drug reaction profiles may differ.Normally, different stereoisomeric forms will have separate ATC codes.Exceptions will be described in the guidelines for the respective ATC groups.A new medicinal substance not clearly belonging to any existing ATC 4th levelgroup of related substances will as a main rule be placed in an X group ("other"group). To avoid a situation of several 4th levels with only one single substance ineach, new 4th levels are as a general rule only established when at least twosubstances with marketing authorisations fit in the group. In addition, a new 4thlevel should be regarded a benefit for drug utilization research. New and innovativemedicinal products will therefore often be classified in an X group and such groupscould be established for only one single substance.Prodrugs are usually assigned separate ATC codes if the dosages used are differentand/or the nonproprietary name of the prodrug and the active drugs are different.Example:J01CA08J01CA11pivmecillinammecillinam2. Classification of plain productsPlain products are defined as:- Preparations containing one active component (including stereoisomericmixtures).- Medicinal products which in addition to one active component contain auxiliarysubstances intended to increase the stability of the preparations (e.g. vaccinescontaining small amounts of antibacterials), increase the duration (e.g. depotformulations) and/or increase the absorption (e.g. different solvents in variousdermatologicals) are also considered as plain products.18