The authors recognize several limitations in this study. Given its observational design, it cannot be definitively concluded that the decrease in HbA1c was due to the initiation of ranolazine. While excluding patients with changes to their antidiabetic medication regimen was done in an effort to minimize confounding factors, it is possible that other factors, such as lifestyle, also could explain changes in HbA1c. It is possible that changes to the DM medication regimen were made but not documented in the EHR. In addition, information on hypoglycemia was not readily available; thus, the safety of ranolazine among patients with DM could not be evaluated fully. Finally, the patient population characteristics may limit external validity.
In this observational study, ranolazine was associated with a statistically significant decrease in HbA1c among veterans with DM, which supports previously published literature.9, 13-15 However, no randomized controlled trials have been performed specifically studying the impact of ranolazine on HbA1c among patient with DM. Ideally, future prospective, randomized placebo-controlled studies will take place to further evaluate the association between ranolazine use and HbA1c lowering.