Drug Corner

_{(featured 27 – 9 – 2020)}

Metformin is the most prescribed medication for diabetes in Australia, and it ranks eighth among all medication prescriptions (Australian Prescriber, 2019). 

Recently, a number of metformin formulations have experienced serious supply shortages in Australia (Brooker, 2020).  This has resulted in the need for brand, dose and formulation substitutions.    Obviously, this requires communication between the prescriber, pharmacy, health care team, and individual for whom the metformin is prescribed.  

During these times, it is especially incumbent on individuals responsible for administering medications to have a strong understanding of the use, action, and effects of metformin as the risk for drug errors or adverse events may increase.   The medication consumer may also require further education regarding their drugs during this time.    

In order to reduce the risk of drug errors associated with brand, dose, or formulation substitution, we’ve provided a brief summary to help you review your metformin drug knowledge.

Metformin – Pharmacokinetics

Absorption ­ – Approximately 70% of immediate-release metformin is absorbed from an oral dose.

Distribution ­ – GIT, liver and kidneys are primary targets.

Metabolism ­ – No known metabolites – metformin is excreted unchanged.

Excretion –  ­ – Almost entirely through the renal system.

 

Metformin – Mechanism of action

Metformin acts to reduce blood glucose through numerous mechanisms, including…

     – reducing uptake of glucose from the GIT

     – reducing the liver’s production of new glucose (gluconeogenesis)

     – improving cell’s uptake and use of glucose (insulin sensitivity)

 

Metformin also has other beneficial effects, including…

     – reducing cardiovascular risk, through

          -reducing inflammation (decreasing cytokines & macrophages)

          – decreasing LDLs

          – reducing weight

 

     – reducing body weight, through

          -reducing appetite (reducing Neuropeptide Y and increasing leptin)

          – reducing lipogenesis (creating fat)

          – increasing lipolysis  (breaking down fat)

 

Metformin – Other important points

     – Should not cause hypoglycaemia (used alone) as it does not increase pancreatic insulin secretion; however, there is some evidence that it may exacerbate hypogylcaemia when used in conjunction with insulin or sulphonylureas (glibenclamide, gliclazide, gliclazide, glimepiride, glipizide).

     – Adverse effects commonly associated with metformin include diarrhoea, nausea, flatulence, and muscle weakness.

     – Serious adverse effects which may be associated with metformin include lactic acidosis and vitamin B12 deficiency.

We try to be safe when administering medications, taking into account all the checks and rights that have formed the cornerstone of our drug education.  However, during these strange times where drug supply issues may influence prescribing and administration considerations, it is even more critical to ensure that our pharmacology knowledge is up to date.

Hopefully, you’ve found this article beneficial to your clinical practice.  Stay tuned for more Drug Corner articles as we make them a regular feature.  

We will also be starting a Youtube channel specifically designed to help students or health care professionals to grow and consolidate important pharmacology and biology concepts.   The plan is to produce short, sharp (1min or less) clips which don’t take too much time out of your already busy day.     

If you have a particular drug or class you’d like us to focus on for a “Drug Corner” or “Biol Bite”, drop us a line on admin@sciencopia.com.au and we’ll do our best to oblige. 

Stay tuned, stay safe, and be a safe practitioner!

References

Australian Prescriber (2019). Top 10 drugs 2018–19. NPS Medicinewise, 42(204). Retrieved from https://www.nps.org.au/australian-prescriber/articles/top-10-drugs-2018-19

Brooker, C. (2020). Metformin Shortage Extends. Australian Journal of Pharmacy. Retrieved from https://ajp.com.au/news/metformin-shortage-extends/

Hales, M., Fisher, R., & Roh. EJ. (2020). Essential Aussie Drugs. Sciencopia. www.sciencopia.com.au

Rena, G., Hardie, D., Pearson, E (2017). The mechanisms of action of metformin. Diabetologia, 60 (9), 1577-1585. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5552828/

Solymár, M. et. al. (2018). Metformin induces significant reduction of body weight, total cholesterol and LDL levels in the elderly – A meta-analysis. PloS one, 13(11), Retrieved from https://doi.org/10.1371/journal.pone.0207947