Guidelines for ATC classification and DDD assignment - WHOCC

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The DDDs for inhalation aerosol and inhalation powder of the same
substance are in most cases given the same DDD value. The DDDs
for inhalation solutions are, however, different from these and
much higher, partly because less amount of the active ingredient
will reach the target organ, and partly because this dosage form
often is used in more severe and unresponsive asthma.
R03AA Alpha- and beta-adrenoreceptor agonists
The DDDs are based on the treatment of asthma.
R03AB Non-selective beta-adrenoreceptor agonists
The DDDs are based on the treatment of asthma.
R03AC Selective beta-2-adrenoreceptor agonists
The DDDs are mainly based on the treatment of asthma.
The DDDs for formoterol and salmeterol inhalation powders are
based on metered dose, even though products containing these
substances could be declared as delivered dose.
R03AH Combinations of adrenergics
See comments to R03AK.
R03AK Adrenergics and other drugs for obstructive airway diseases
All adrenergics for inhalation in combination with other drugs for
obstructive airway diseases are classified in this group.
The preparations are classified at 5th levels according to the adrenergic
component. At each 5th level different drugs for obstructive airway
diseases may occur.