Metformin, an oral hypoglycemic agent has been found to exhibit antimicrobial activity against various Gram positive and Gram negative bacteria, fungi, parasites, and viruses.¹ A systematic review analyzed the effects of metformin on a wide range of pathogens and reported good efficacy as an antimicrobial agent in patients with tuberculosis.² The mechanisms which may underlineits anti-tubercular activity are activation of adenosine activated protein kinase and mitochondrial production of reactive oxygen species, acceleration of phagosome-lysosome fusion, improved immune response, increased CD 4 and CD 8 cells, rise inmycobacteria specific interferon secretion by CD 8 cells, and decreased expression of inflammatory genes. The researchers have demonstrated that in patients with diabetes mellitus and tuberculosis, in whom antitubercular treatment was given along with metformin as an antidiabetic drug, had relatively better prognostic outcome compared to their counterparts who were not administered metformin.¹

Besides, experimental studies have shown the role of metformin in increasing survival in models of endotoxemia by diminishing levels of proinflammatory cytokines. Laboratory studies conducted in the past have reported the efficacy of this agent against multiple pathogens, including Trichinella spiralis, Staphylococcus aureus, Pseudomonas aeruginosa, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus.^1,2

Furthermore, easing in United States Food and Drug Administration guidelines pertaining to administration of metformin in patients with kidney disease, and reduced anxiety about patient safety in terms of lactic acidosis, enhance the probability of expansion of therapeutic profile of metformin to treatment of infectious agents.² Some studies have reported that use of this drug can reduce the incidence and severity of infections and improve outcomes.¹ One such study assessed the effects of metformin in vivo in a Helicobacter pylori-infected model. It was observed that H. pylori survival and growth reduced in the presence of metformin. Moreover, metformin-treated models had remarkably fewer bacteria in their stomach in comparison to the untreated models.³

Therefore, in addition to its traditional effects on glucose metabolism, metformin displays antimicrobial actions in patients with tuberculosis and other infections encountered in vitro and in vivo.²

References

1. Patil TR, Patil ST, Patil S, et al. Antimicrobial Potential of Metformin. International Journal of Pharmacognosy and Phytochemical Research 2019;11(3);230-234.
2. Malik F, Mehdi SF, Ali H, et al. Is metformin poised for a second career as an antimicrobial? Diabetes Metab Res Rev. 2018 May;34(4):e2975.
3. Courtois S, Bénéjat L, Izotte J, et al. Metformin can inhibit Helicobacter pylori growth. Future Microbiol. 2018 Nov;13:1575-1583.