Average Number of Drug Classes Used by Seniors on Public Drug Programs
The indicator measures the average number of drug classes seniors take over the course of a year. Seniors with multiple chronic conditions often require treatment with multiple medications. Using a higher number of drugs is associated with a higher risk of adverse drug reactions and other adverse events, like drug interactions. As some drugs are taken consistently over long periods of time and some (such as antibiotics) are taken for shorter durations, this indicator should not be interpreted as the number of drugs seniors take at one time.
The total number of distinct drug classes for each senior (age 65 and older), summed for all seniors on public drug programs, divided by the number of seniors with at least one claim accepted by a public drug program over a defined period (usually one year)
Total number of seniors with at least one claim accepted by a public drug program
Number of distinct drug classes (as defined by WHO ATC classification level 4) with at least one claim accepted by a public drug program for a senior, summed for all seniors on public drug programs
Methodology
Name
Average Number of Drug Classes Used by Seniors on Public Drug Programs
Short/Other Names
Not applicable
Description
This indicator measures the average number of distinct drug classes (as defined by WHO ATC classification level 4) with at least one claim accepted by a public drug program for a senior (age 65 and older).
Notes
WHO: World Health Organization
ATC: Anatomical Therapeutic Chemical
Rationale
Using a higher number of drugs is associated with a higher risk of adverse drug reactions and other adverse events, like drug interactions.
Drug class was selected rather than drug to avoid the impact of seniors switching between drugs for the same condition (it is unlikely that two drugs from the same class would be used at the same time).
This indicator can be used to see whether the average number of drugs a senior is using changes over time and whether there are different prescribing patterns as seniors age.
Interpretation
The indicator measures the average number of drug classes seniors take over the course of a year. Seniors with multiple chronic conditions often require treatment with multiple medications. Using a higher number of drugs is associated with a higher risk of adverse drug reactions and other adverse events, like drug interactions. As some drugs are taken consistently over long periods of time and some (such as antibiotics) are taken for shorter durations, this indicator should not be interpreted as the number of drugs seniors take at one time.
HSP Framework Dimension
Health system outputs: Appropriate and effective
Areas of Need
Living With Illness, Disability or Reduced Function
Targets/Benchmarks
Not applicable
Available Data Years
to (calendar years)
Geographic Coverage
- Newfoundland and Labrador
- Prince Edward Island
- New Brunswick
- Nova Scotia
- Quebec
- Ontario
- Manitoba
- Saskatchewan
- Alberta
- British Columbia
- Yukon
Reporting Level/Disaggregation
- Province/Territory
Indicator Results
Update Frequency
Whenever it is required for analytical product or data request
Latest Results Update Date
Updates
Not applicable
Description
The total number of distinct drug classes for each senior (age 65 and older), summed for all seniors on public drug programs, divided by the number of seniors with at least one claim accepted by a public drug program over a defined period (usually one year)
Type of Measurement
Average or mean
Denominator
Description:
Total number of seniors with at least one claim accepted by a public drug program
Inclusions:
- All seniors (age 65 years and older)
Exclusions:
- All non-seniors (age younger than 65 years)
Numerator
Description:
Number of distinct drug classes (as defined by WHO ATC classification level 4) with at least one claim accepted by a public drug program for a senior, summed for all seniors on public drug programs
Inclusions:
- All seniors (age 65 years and older)
Exclusions:
- All non-seniors (age younger than 65 years)
Method of Adjustment
Not applicable
Not applicable
Adjustment Applied
None
Geographic Assignment
Place of service
Data Sources
- NPDUIS Database
Caveats and Limitations
The National Prescription Drug Utilization Information System (NPDUIS) Database includes claims accepted by public drug programs, either for reimbursement or toward a deductible. Claims are included regardless of whether or not the patient actually used the drugs.
The NPDUIS Database does not include information regarding
- Prescriptions that were written but never dispensed
- Prescriptions that were dispensed but for which the associated drug costs were not submitted to or accepted by the public drug programs
- Diagnoses or conditions for which prescriptions were written
The NPDUIS Database contains claims data from public drug programs in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador and Yukon. The First Nations and Inuit Health Branch (FNIHB), a federal drug program, also submits data, which comes from all Canadian provinces and territories (including those not listed above).
Trending Issues
All data is not available for all years:
- Manitoba, Saskatchewan, Alberta, New Brunswick: From January 2000
- Nova Scotia: From April 2001
- Prince Edward Island: From April 2004
- British Columbia: From January 2006
- Yukon: From January 2007
- Newfoundland and Labrador: From April 2008
- Ontario: From April 2010
- First Nations and Inuit Health Branch: From October 2010
References
Not applicable
How to cite:
Canadian Institute for Health Information. Average Number of Drug Classes Used by Seniors on Public Drug Programs . Accessed April 25, 2025.
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Comments
Not applicable