Acarbose may not have a cardioprotective effect that is similar to metformin when used as first-line therapy for diabetes, according to a new retrospective study.1
This study analyzed 17,366 patients who initiated acarbose therapy and 230,023 who initiated metformin therapy. Both nephropathy and diabetes complication severity index were strongly associated with the patients who initiated acarbose.
The study stated that the “acarbose initiators were older, and had a higher proportion of ischemic heart disease, cerebrovascular disease, hypertension, and dyslipidemia, and a higher diabetes complication severity index.”
Hospitalization for any cardiovascular (CV) event, such as myocardial infarction (MI), congestive heart failure or ischemic stroke, served as the primary outcome.
During an average follow-up period of 1.15 years, 3,672 cases in the acarbose group and 34,717 cases in the metformin group had an outcome occurrence, according to the data.
Intent-to-treat analyses showed that acarbose was associated with a higher risk for any CV event (adjusted HR=1.05; 95% CI, 1.01-1.09), heart failure (HR=1.08; 95% CI, 1.00-1.16) and ischemic stroke (HR=1.05; 95% CI, 1.00-1.10). Subgroup analyses did not find significant differences in subgroups stratified by sex, age, and underlying diseases.
The study authors explained that the study’s huge sample size, which included almost all newly-diagnosed type 2 diabetes patients in Taiwan, and its sufficient number of CV events allowed incidences to be precisely estimated.
The study authors also stated, however, that their study was limited because it was an observational cohort study and not a randomized controlled trial. Further, its follow-up period was very short.
The study found that acarbose doesn’t come out as better than metformin. It’s possible that acarbose might not be as good as metformin, but you have to take into consideration the lack of randomization and the sicker population. The patients who went on acarbose had more diabetic complications and more cardiovascular disease.
This study is probably not a reason to change existing practice.
It is important to note that the patients who received acarbose were more likely to have renal dysfunction than those who initiated metformin. The study may have inadvertently enriched for cardiovascular disease in the acarbose group.
The short follow-up time is also important to note.
We still don’t know if acarbose or metformin is better. This study is not a stinging indictment of acarbose. Metformin is considered the frontline treatment in the United States for type 2 diabetes, and this study does not change that in any way.
There are a lot of good data in placebo-controlled trials that indicate acarbose is an excellent drug. While this study might give pause, it would not force me to move to metformin if I were taking acarbose.
Robert W. Lash, MD
Incoming Chair of the Endocrine Society’s Clinical Affairs Core Committee
Professor of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes
University of Michigan Health System