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

Abstract

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.