In 1950, Stern et al discovered the clinical usefulness of metformin while working in Paris (France). They observed that the dose–response of metformin was related to its glucose lowering capacity and that metformin toxicity also displayed a wide security margin.2
Since then, the efficacy and safety of metformin have been shown in numerous studies. One of the earliest studies was the landmark United Kingdom Prospective Diabetes Study (UKPDS) in 1998, which first showed the cardiovascular benefit of metformin.1
Current guidelines from the American Diabetes Association/European Association for the Study of Diabetes, the American Association of Clinical Endocrinologists/American College of Endocrinology and South Africa recommend early initiation of metformin as a first-line drug for monotherapy and combination therapy for patients with T2DM.2
This recommendation is based primarily on metformin’s glucose-lowering effects, relatively low cost, and generally low level of side effects, including the absence of weight gain.2
The older, immediate-release formulation of metformin does have some limitations, with incidence of gastrointestinal (GI) adverse effects restricting the dose in some patients, forming a barrier to treatment adherence, and subsequent glycaemic control. However, the second-generation extended-release formulation (ER) has the potential to overcome these challenges. ER metformin improves GI tolerability, allows once-daily dosing, and is currently available in multiple branded and generic formulations.3,4
Maximum plasma metformin concentrations are reached more slowly with the extended-release formulation compared with conventional immediate-release metformin, although both provide similar exposure at a given total daily dose.4
ER metformin is as effective as immediate-release metformin in patients newly started on metformin and those switched from the immediate-release formulation, with similar weight-neutral effects.4
Tolerability is generally comparable, although patients switched from the immediate-release formulation – even those switched due to GI intolerance – are often better able to tolerate the ER formulation.4
Based on studies of ER formulations in other disease states, metformin ER formulation has the potential to improve patient adherence with a simpler dosing regimen and increased tolerability.4
Increased adherence may result in greater glycaemic control, and in turn, improve outcomes and lower health care usage and costs. ER metformin provides an appropriate option for patients with T2DM who require several medications to achieve glycaemic control or manage comorbid conditions, and for those who have GI intolerance with the immediate-release formulation.4
REFERENCES
1. Bailey CJ. Metformin: historical overview. Diabetologia, 2017.
2. Rojas LBA and Gomes MB. Metformin: an old but still the best treatment for type 2 diabetes. Diabetol Metab Syndr, 2013.
3. Chacra AR. Evolving metformin treatment strategies in type-2 diabetes: from immediate-release metformin monotherapy to extended-release combination therapy. Am J Ther, 2014.
4. Jabbour S and Ziring B. Advantages of Extended-Release Metformin in Patients with Type 2 Diabetes Mellitus. Postgraduate Medicine, 2015.
