[Defined daily doses in drugs with combinations of active principles: differences between three calculation methods.]

Area of Science:

• Pharmacoeconomics
• Drug Utilization Studies
• Pharmaceutical Policy

Background:

• Defined Daily Dose (DDD) is crucial for drug utilization studies.
• Combined pharmaceutical products complicate accurate DDD calculation.
• Variations in DDD calculation methods impact drug consumption analysis.

Purpose of the Study:

• Compare different methods for calculating DDD.
• Evaluate DDD calculation for single-ingredient and combination drugs.
• Assess the impact of calculation methods on drug consumption data.

Main Methods:

• Utilized prescription billing data from Catalonia (2019).
• Compared three DDD calculation methods: WHO standard, main ingredient, and all active ingredients.
• Analyzed non-insulin hypoglycaemic drugs (nIHG) and obstructive respiratory pathology (ORP) drugs.
• Employed Wilcoxon test for paired data analysis.

Main Results:

• Significant discrepancies in total DDD and subgroup participation were observed.
• Differences reached 17% for nIHG and 118% for ORP drugs.
• Calculating DDD with all active ingredients offered a more accurate consumption estimate.

Conclusions:

• The method considering all active ingredients in combination products is most valuable.
• This approach enhances pharmacoepidemiological management.
• Accurate drug consumption data is vital for healthcare decision-making.