To the Editor:

We read with great interest the editorial published in the last issue of Nefrología titled: “About the discrepancies between clinical consensus documents, clinical practice guidelines, and legal regulations in the treatment of type 2 diabetes mellitus”,1 and we would like to make a brief commentary on this article.

Firstly, we wish to state that this editorial inspired a great deal of interest since it updates and includes several innovative aspects, such as indications for use, based on the summary of characteristics information, for oral anti-diabetic medications (OAD), insulin, and glucagon-like peptide analogues, which are used in the treatment of patients with type 2 diabetes mellitus (DM2); however, we would also like to know the opinion of the authors regarding the legal aspects of the use of these drugs, especially in the case of metformin in renal failure patients.

In the section of the editorial dedicated to metformin, the authors specify that this molecule is eliminated through the kidneys, which supports the contraindication stated on the summary of characteristics for use in patients with creatinine clearance rates <60ml/min, due to the risk of lactic acidosis. However, it can be used in patients with glomerular filtration rates (GFR) of as low as 30ml/min/1.73m2 [sic].

Based on the recommendations provided by the NICE guidelines and studies such as Shaw et al. and Lipska et al., the authors later suggest a contraindication for metformin in patients with GFR<30ml/min/1.73m2 and utilisation with precaution in patients with GFR<45ml/min/1.73 with risk factors for developing lactic acidosis, allowing for its use in patients with moderate chronic kidney disease (estimated GFR: 30-50ml/min/1.73m2).1

We published an earlier article in the journal of Nefrología on this topic, in which we bring attention to the need for health care professionals that prescribe OAD, especially metformin (this being the OAD indicated in the initial treatment of patients with DM2 and the most heavily used), to be able to do so within the legal framework that regulates its use based solely on the drug summary of characteristics, not guidelines, consensus documents, or isolated studies.2

As such, and after reading the editorial in question, we continue with the same doubts that prompted our article. Is it illegal to administer metformin in patients with creatinine clearance rates <60ml/min, as described by the drug summary of characteristics and as recommended by the Spanish Society for Diabetes, which also contraindicates its use in patients with a GFR<60ml/min/1.73m2?3

In addition, nephrologists treat a large number of diabetic patients with various levels of renal failure who are sent from other specialists and later transferred back to them. Should we prescribe medications outside of the guidelines established in their respective summary of characteristics to these patients, without generating potential legal conflicts in a medical society that is becoming more and more judicialised?

With this in mind, we would like to know the opinion of the authors of the aforementioned editorial, and would also like to highlight the need for Spanish research groups studying diabetes to contemplate these aspects when elaborating guidelines or research documents that serve as reference materials for proper medical practice.

Conflicts of interest

The authors state that they have no potential conflicts of interest related to the content of this article.