Narrative review of data supporting alternate first-line therapies over metformin in type 2 diabetes

Metformin has been the first-line treatment for type 2 diabetes mellitus as monotherapy or concomitantly with other glucose-lowering therapies due to its efficacy, safety, and affordability. Recent studies on the cardioprotective and renoprotective benefits of glucagon-like peptide-1 receptor agonists (GLP-1 RA) and sodium-glucose cotransporter-2 inhibitors (SGLT-2i) have influenced guidelines on diabetes management to consider these newer agents as alternative first-line therapies. This paper explores the literature supporting the use of these newer medications alone as a first-line agent in place of metformin.

A review of citations from the most recent guidelines along with a literature search via PubMed was completed to review (1) what, historically, made metformin first-line (2) if newer agents’ benefits remain when used without metformin (3) how newer agents compare against metformin when used without it.

Evaluation of the historical literature was completed to summarize the key findings that support metformin as a first-line therapy agent. Additionally, an assessment of the literature reveals that the benefits of these two newer classes are independent of concomitant metformin therapy. Finally, studies have demonstrated that these newer agents can be either non-inferior or sometimes superior to metformin when used as monotherapy.

GLP-1 RA and SGLT-2i can be considered as first line monotherapies for select patients with high cardiovascular risks, renal disease, or weight loss requirements. However, pharmacoeconomic considerations along with lesser long-term safety outcomes should limit these agents’ use in certain patients as the management of diabetes continues to transition towards shared-decision making.