Retrospective Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Nephrol. Jul 6, 2016; 5(4): 367-371
Published online Jul 6, 2016. doi: 10.5527/wjn.v5.i4.367
Metformin associated lactic acidosis in Auckland City Hospital 2005 to 2009
Imad Haloob, Janak R de Zoysa
Imad Haloob, Department of Medicine, Bathurst Base Hospital, Bathurst, New South Wales 2795, Australia
Janak R de Zoysa, Department of Renal Medicine, North Shore Hospital, Auckland 0740, New Zealand
Janak R de Zoysa, Waitemata Clinical School, Faculty of Medicine and Health Sciences, The University of Auckland, Auckland 0740, New Zealand
Author contributions: Haloob I conceived the study, performed data collection and wrote the initial manuscript while working at Auckland Hospital; de Zoysa JR helped design the study, reviewed data collection and reviewed and revised the manuscript while working at Auckland Hospital.
Institutional review board statement: This retrospective review was approved by the Northern X Regional Ethics Committee (NTX/EXP).
Informed consent statement: Patients were not required to give informed consent to the study because the analysis used anonymous, de-identified clinical data.
Conflict-of-interest statement: There are no conflicts of interest in the publication of this paper.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dr. Janak R de Zoysa, Clinical Director, Department of Renal Medicine, North Shore Hospital, Waitemata District Health Board, 122 Shakespeare Road, Takapuna, Auckland 0740, New Zealand. janak.dezoysa@waitematadhb.govt.nz
Telephone: +64-9-4868900 Fax: +64-9-4423218
Received: January 27, 2016
Peer-review started: January 27, 2016
First decision: February 29, 2016
Revised: March 21, 2016
Accepted: April 21, 2016
Article in press: April 22, 2016
Published online: July 6, 2016
Processing time: 154 Days and 0.6 Hours
Abstract

AIM: To determine the incidence, clinical characteristics and outcomes of patients with metformin associated lactic acidosis (MALA).

METHODS: Auckland City Hospital drains a population of just over 400000 people. All cases presenting with metabolic acidosis between July 2005 and July 2009 were identified using clinical coding. A retrospective case notes review identified patients with MALA. Prescribing data for metformin was obtained from the national pharmaceutical prescribing scheme.

RESULTS: There were 42 cases of metabolic lactic acidosis over 1718000 patient years. There were 51000 patient years of metformin prescribed to patients over the study period. There were thirty two cases of lactic acidosis due to sepsis, seven in patients treated with metformin. Ten cases of MALA were identified. The incidence of MALA was estimated at 19.46 per 100000 patient year exposure to metformin. The relative risk of lactic acidosis in patients on metformin was 13.53 (95%CI: 7.88-21.66) compared to the general population. The mean age of patients with MALA was 63 years, range 40-83 years. A baseline estimated glomerular filtration rate was obtained in all patients and ranged from 23-130 mL/min per 1.73 m2. Only two patients had chronic kidney disease G4. Three patients required treatment with haemodialysis. Two patients died.

CONCLUSION: Lactic acidosis is an uncommon but significant complication of use of metformin which carries a high risk of morbidity.

Keywords: Acute kidney injury; Lactic acidosis; Metformin

Core tip: Metformin is an effective therapy for type 2 diabetes mellitus. Although few side effects are described in clinical trials, here, we describe observational evidence that suggests that use of metformin is associated with an increased risk of lactic acidosis. We recommend dose reduction in the elderly, withholding the drug if an intercurrent illness occurs and that metformin be halted in patients with chronic kidney disease G4.