Background Metformin is one of the most commonly prescribed drugs for the treatment of type 2 DM. A potential complication of metformin is lactic acidosis (LA). This potential increased risk remains controversial.

Purpose To evaluate the occurrence of LA in type 2 DM patients treated with metformin. To study the prevalence of acute renal failure in these patients and the final outcome.

Material and methods Retrospective observational study in a general hospital. Discharge certificates including codes for LA and DM (ICD–9) during 2013 were classified; we selected those under treatment with metformin.

Exclusion criteria: Patients with decompensated diabetes/ketoacidosis and patients with chronic renal failure.

Results 126 discharge certificates coding LA, DM, and treatment with metformin were classified. 87 of these patients met some exclusion criteria. Among the 39 remaining patients, in 14 of them “LA related to the use of metformin” was specifically described in the discharge certificate.

Distribution in sex and age was 58% men and 81 ± 10 years.

In 100% of the cases acute renal failure was observed.

One patient died, the rest of them were discharged after a median stay of 8 ± 3 days.

According to data provided by the health service, 9,713 patients were being treated with metformin in our area. This equates to an incidence of 14/10,000 patient-years.

Conclusion We found a much higher incidence of LA than that described in the literature. This potentially fatal complication should be avoided by controlling risk factors. We consider education of physicians and patients essential; in this point, pharmacists have an important role.

References and/or Acknowledgements

1. Lalau JD, Race JM. Lactic acidosis in metformin therapy: searching for a link with metformin in reports of metformin associated lactic acidosis. Diabetes Obes Metab 2001;3:195–201

2. Misbin RI, Green L, Stadel BV, et al. Lactic acidosis in patients with diabetes treated with metformin. N Engl J Med 1998;338:265–6

References and/or AcknowledgementsNo conflict of interest.