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Length of initial prescription at hospital discharge and long-term medication adherence for elderly, post-myocardial infarction patients: a population-based interrupted time series study

Schwalm JD, Ivers NM, Bouck Z, Taljaard M, Natarajan MK, Nguyen F, Hijazi W, Thavorn K, Dolovich L, McCready T, O'Brien E, Grimshaw JM. BMC Med. 2022; 20(1):213. Epub 2022 Jun 21. DOI:

Background — Preliminary evidence suggests that providing longer duration prescriptions at discharge may improve long-term adherence to secondary preventative cardiac medications among post-myocardial infarction (MI) patients. We implemented and assessed the effects of two hospital-based interventions—(1) standardized prolonged discharge prescription forms (90-day supply with 3 repeats for recommended cardiac medications) plus education and (2) education only—on long-term cardiac medication adherence among elderly patients post-MI.

Methods — We conducted an interrupted time series study of all post-MI patients aged 65–104 years in Ontario, Canada, discharged from hospital between September 2015 and August 2018 with ≥ 1 dispensation(s) for a statin, beta blocker, angiotensin system inhibitor, and/or secondary antiplatelet within 7 days post-discharge. The standardized prolonged discharge prescription forms plus education and education-only interventions were implemented at 2 (1,414 patients) and 4 (926 patients) non-randomly selected hospitals in September 2017 for 12 months, with all other Ontario hospitals (n = 143; 18,556 patients) comprising an external control group. The primary outcome, long-term cardiac medication adherence, was defined at the patient-level as an average proportion of days covered (over 1-year post-discharge) ≥ 80% across cardiac medication classes dispensed at their index fill. Primary outcome data were aggregated within hospital groups (intervention 1, 2, or control) to monthly proportions and independently analyzed using segmented regression to evaluate intervention effects. A process evaluation was conducted to assess intervention fidelity.

Results — At 12 months post-implementation, there was no statistically significant effect on long-term cardiac medication adherence for either intervention—standardized prolonged discharge prescription forms plus education (5.4%; 95% CI − 6.4%, 17.2%) or education only (1.0%; 95% CI − 28.6%, 30.6%)—over and above the counterfactual trend; similarly, no change was observed in the control group (− 0.3%; 95% CI − 3.6%, 3.1%). During the intervention period, only 10.8% of patients in the intervention groups received ≥ 90 days, on average, for cardiac medications at their index fill.

Conclusions — Recognizing intervention fidelity was low at the pharmacy level, and no statistically significant post-implementation differences in adherence were found, the trends in this study—coupled with other published retrospective analyses of administrative data—support further evaluation of this simple intervention to improve long-term adherence to cardiac medications.

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