Postal address:
Norwegian Institute of Public Health
WHO Collaborating Centre for Drug Statistics Methodology
Postboks 222 Sk°yen
0213 Oslo

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0473 Oslo

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A formulation approved both for use in the eye/ear is classified in S03. Formulations approved for eye, ear and nose are also classified in S03. Formulations only licensed for use in the eye or the ear are classified in S01 and S02, respectively.


Most of the drugs in this group are topical preparations. Systemic preparations with clear ophthalmological indications are also classified in this group.
Small amounts of antiseptics in eye preparations do not influence the classification, e.g. benzalconium.
See also S03 - Ophthalmological and otological preparations.

DDDs have been assigned for antiglaucoma preparations only.


This group comprises preparations for local and systemic treatment of glaucoma.
Drugs used for producing miosis are classified in this group, even if the main indication is not glaucoma.

The DDDs are based on single dose (or single package) and administration frequencies. A single dose is defined as two eye drops (one in each eye) corresponding to 0.1 ml. For eye drops administered once daily the DDD is 0.1 ml, for eye drops administered twice daily the DDD is 0.2 ml, etc. For single use packages one dose is the volume of one package. This also applies for combinations. In eye ointments one dose corresponds to about 10 mm (20 mg) per eye thus corresponding to 40 mg for both eyes.

S01EC Carbonic anhydrase inhibitors

Carbonic anhydrase inhibitors used for different indications are classified in this group.
Diclofenamide for treatment of periodic paralysis is classified here.

The DDDs are based on the average recommended doses in the treatment of chronic glaucoma.

List of abbreviations

Last updated: 2024-01-26