Guidelines for ATC classification and DDD assignment - WHOCC

2. Combination products
The DDDs assigned for combination products are based on the main principle of
counting the combination as one daily dose, regardless of the number of active
ingredients included in the combination. If a treatment schedule for a patient
includes e.g. two single ingredient products, then the consumption will be measured
by counting the DDDs of each single ingredient product separately. If, however, a
treatment schedule includes a combination product containing two active
ingredients, then the calculated consumption measured in DDDs will normally be
lower since the DDD for the combination will be counted.
Example I:
Treatment with two products, each containing one active ingredient:
Product A: Tablets containing 20 mg of substance X (DDD = 20 mg)
Product B: Tablets containing 25 mg of substance Y (DDD = 25 mg)
The dosing schedule 1 tablet of A plus 1 tablet of B daily will be calculated as a
consumption of 2 DDDs.
Example II:
Treatment with a combination product containing two active ingredients:
Product C: Tablets containing 20 mg of substance X and 12.5 mg of substance Y.
The DDD of the combination products is assigned as 1 UD = 1 tablet.
The dosing schedule 1 tablet of C daily will be calculated as 1 DDD (even though it
will be equivalent to 1.5 DDD of the single active ingredients).
The following principles for assigning DDDs to combination products apply:
1. For combination products (other than the combination products used in
hypertension, see point 2 below) where the ATC code identifies the main
ingredient (i.e. for the 50- and 70-series combinations and for some 4 th level
combinations), the DDD for the combination product should be equal to the
DDD for the main active ingredient.
2. For combination products used for treatment of hypertension (i.e. ATC group
C02L, C02N, C03E, C07B-F, C08 and C09), DDDs are based on the average
number of dosing intervals per day. This means that: 1 tablet is the DDD for
combinations given once daily, whereas 2 tablets is the DDD for combinations
given twice daily and 3 tablets is the DDD for combinations given three times
daily etc. This principle means that the assigned DDDs may differ from the DDD
assigned for the main active ingredient (according to ATC code).
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