Do Provincial Formulary Restrictions Explain Differential Uptake of Sodium-Glucose Co-Transporter-2 Inhibitors in Adults with Diabetes and Cardiovascular Disease in Canada? A Retrospective Cohort Study of Pharmacy Claims.

Background: Ontario listed SGLT-2 inhibitors (SGLT2i) as regular public drug benefits for adults age ≥ 65, while other Canadian provinces providing benefits for SGLT2i implemented special authorization restrictions. We hypothesized that special authorization led to lower SGLT2i use among older adults with diabetes and cardiovascular disease (CVD) in other provinces (Alberta, Manitoba, New Brunswick, and Saskatchewan), compared to Ontario.

Methods: Retrospective cohort study of adults with diabetes and CVD, age ≥ 65 years, discharged from hospital April 1, 2016 to March 31, 2019, in five Canadian provinces. Data were obtained from a national discharge database linked with public pharmacy claims. We followed individuals from discharge until March 31, 2019 for SGLT2i uptake. We also examined SGLT2i discontinuation and sulfonylurea uptake as control outcomes. Fine-Gray hazard models were adjusted for comorbidities and area-level socio-demographics.

Results: Of 161,249 individuals (average age 78 years, 42% female, median follow-up 1.8 years), 68% were from Ontario, and 32% were from other provinces. Cumulative SGLT2i uptake at 6 months was 2.2% in Ontario vs 0.7% in other provinces, with adjusted hazard ratio [aHR] = 2.72, 95% CI [2.56-2.94], p < 0.001). Ontario residents had similar SGLT2i discontinuation or sulfonylurea uptake compared to other provinces. Other predictors of SGLT2i uptake were identified.

Conclusions: There was an interprovincial disparity in SGLT2i uptake in older adults with diabetes and cardiovascular disease, in whom SGLT2i are now indicated for cardio-kidney benefit. Special authorization restrictions should be flexibly and rapidly re-assessed and revised as new evidence of clinical benefits become available.