(3) Rates per user per year
§(assuming actual number of users of Ampicillin of 10,000 users)
§# of DDDs per year per user
= 750,000 DDDs per year / 10,000 users
= 75 DDDs per user per year
§
§This is interpreted as the average duration of treatment (number of days per year) for every user of the drug/drug class