Royal College of Surgeons in Ireland
Fixed-dose combination antihypertensives and risk of medication errors.pdf (301.17 kB)

Fixed-dose combination antihypertensives and risk of medication errors

Download (301.17 kB)
journal contribution
posted on 2021-08-19, 11:04 authored by Frank MoriartyFrank Moriarty, Kathleen BennettKathleen Bennett, Tom FaheyTom Fahey

Objective: While fixed-dose combinations (FDC) can improve adherence, they may add complexity to the prescribing/dispensing process, potentially increasing risk of medication errors. This study aimed to determine if prescriptions for antihypertensive FDCs increase the risk of therapeutic duplication and drug-drug interactions (DDI).

Methods: This retrospective observational study used administrative pharmacy claims data from the Irish Primary Care Reimbursement Service. Prescriptions dispensed to adults in 2015 were included if they contained an antihypertensive FDC, or the same drugs prescribed separately. The outcomes were therapeutic duplication and potentially serious DDI involving FDC drugs. Relative risk (RR) of these outcomes, adjusted for prescription and patient factors, was determined using generalised linear models with Poisson distributions and propensity score matching.

Results: This study included 307 833 FDC prescriptions (67.0%) and 151 632 separate component prescriptions. Half of patients prescribed FDCs were female with a mean age of 67.1 (SD 12.5) years and, compared with separate component prescriptions, FDCs were less often coprescribed with other cardiovascular medications. Therapeutic duplication occurred in 0.8% of prescriptions, most often involving calcium channel blockers, and 10.6% contained a DDI (most often amlodipine and simvastatin). The RR of therapeutic duplication on FDC prescriptions compared with separate component prescriptions was 1.46 (95% CI 1.17 to 1.83) and the adjusted RR was 2.06 (95% CI 1.64 to 2.60). For DDIs, there was no significant difference between FDC and separate component prescriptions after confounder adjustment.

Conclusions: This study found FDCs were associated with increased risk of duplication. When considering prescribing FDCs, this safety consideration should be weighed against potential benefits.


Health Research Board (HRB) in Ireland through the HRB Centre for Primary Care Research (grant number HRC/2014/1)

HRB (grant number RL/15/1579)



The original article is available at

Published Citation

Moriarty F, Bennett K, Fahey T. Fixed-dose combination antihypertensives and risk of medication errors. Heart. 2019;105(3):204-209.

Publication Date

2 August 2018

PubMed ID



  • HRB Centre for Primary Care Research
  • General Practice
  • Data Science Centre

Research Area

  • Population Health and Health Services




  • Published Version (Version of Record)