Trends in Drug Duplications in Swedish Older Adults: A Nationwide Register Study from 2006 to 2021.

Background: Drug duplication (DD), the use of two identical drugs simultaneously, is a medication error increasing the risk of adverse drug events. We describe the trends and implicated drugs in potential DD in older adults in Sweden from 2006 to 2021.

Methods: We conducted a register-based, repeated cross-sectional study of all older adults (aged ≥65 years) dispensed drugs at a community pharmacy in 2006-2021. DD was defined as a ≥30-day overlap of two dispensations of drugs with the same 5th level (chemical substance) Anatomical Therapeutic Chemical (ATC) classification, but with different brand names, within a 3-month period each year.

Results: Among Swedish older adults with ordinary prescriptions (i.e. multidose excluded; n ≈ 1,200,000-1,600,000 per year), the prevalence of potential DD increased from 5.2% to 10.6% in 65- to 79-year-olds and from 7.0% to 11.7% in those aged ≥80 years. The drug groups (ATC level 3; pharmacological subgroup) most frequently implicated in DD in 2006 were β-blocking agents, angiotensin-converting enzyme (ACE) inhibitors, and calcium channel blockers, and in 2021 Vitamin B12 and folic acid, β-blocking agents and angiotensin II receptor blockers.

Conclusions: DD represents a common but unnecessary and potentially hazardous medication error. Our results indicate that during the last two decades, the prevalence has almost doubled in older adults with ordinary prescriptions, reaching 11% in 2021. More national efforts are needed to revert this trend, including a nationally available complete drug list for all patients, and prescriber support to detect DD.