What are the advantages and disadvantages of DDDs?

Drug utilisation analysis has used DDDs as the key measure since the 1970s but DDDs were never developed specifically to monitor the impact of antimicrobial stewardship interventions.

So what are the advantages and disadvantages of DDDs as a metric?

Advantages	Disadvantages
Internationally recognised as assigned and published by WHO.	Unsuitable for paediatric settings as DDD defined as average dose in adults.
Once set by WHO a DDD is not often changed – this allows assessment of prescribing over time.	Can over or underestimate antibiotic use as do not account for alternative dosing regimes due to renal dysfunction, obesity etc.
Easy to produce information on antibiotic use expressed in DDD for ward, unit or hospital.	Bias against combination therapy – use of three narrow spectrum antibiotics rather than one broad spectrum antibiotic will result in three times as many DDD being used for the same infection.
Ability to compare antibiotic use in a standardised way between wards or hospitals.	May not reflect dose used for a particular infection.