Chemical Structure:
Class of drug: Biguanide (Antidiabetic)
Drug action/mode of action:
Metformin works mainly by decreasing gluconeogenesis and by increasing peripheral utilization of glucose. It acts only in the presence of endogenous insulin so it is effective only if there are some residual functioning pancreatic islet cells.
Medicinal forms: Tablets, Modified-release tablets, and Oral solution
Some brands available: Glucophage, Enaphage, Metformin-Denk, Glumetza, Fortamet, Riomet, Glucophage XR.
Indications and dose:
Type 2 diabetes mellitus
Adult and Child(10-17years)
Initially 500 mg once daily, and adjusted at intervals of at least 1 week. Up to maximum daily dose (2g) to be given in 2–3 divided doses.
Polycystic ovary syndrome
Initially 500 mg once daily for 1 week, dose to be taken with breakfast, then 500 mg twice daily for 1 week, dose to be taken with breakfast and evening meal, then 1.5–1.7 g daily in 2–3 divided doses.
Unlicensed use: Not licenced for use in children below 10 years and for polycystic ovary syndrome.
Contra-indications: Diabetic ketoacidosis, Lactic acidosis.
Cautions to the use of metformin:
Congestive heart failure, renal impairment, hepatic(liver) impairment, elderly, risk of dehydration and hypoxia (low oxygen supply to tissues).
Interactions of Metformin:
Alcohol – increases the risk of lactic acidosis
Cimetidine – increases exposure to metformin
Dolutegravir – increases exposure to metformin
Side-effects of metformin:
· Abdominal pain
· Decreased appetite
· Diarrhoea (usually transient)
· Gastrointestinal disorder
· Nausea
· Altered taste
· Vomiting
Pregnancy: Can be used in pregnancy.
Breast feeding: Can be used during breast-feeding.
Hepatic impairment: Avoid or withdraw if tissue hypoxia occurs or is likely.
Renal impairment: Avoid if eGFR is less than 30 mL/minute/1.73 m2.
Monitoring requirements: Determine renal function before treatment and at least annually
Patient and career advice on the use of metformin:
Patients and their careers should be informed of the risk of lactic acidosis and told to seek immediate medical attention if symptoms such as dyspnoea, muscle cramps, abdominal pain, hypothermia, or asthenia occur.
Other drugs in class:
Metformin is the only available biguanide approved for use.
WRITTEN AND EDITED RESPECTIVELY BY:
MPSGH, MRPharmS, MPhil.
Isaiah Amoo is a practicing community pharmacist in good standing with the Pharmacy Council of Ghana who has meaningful experience in academia and industrial pharmacy. He is a member of the Royal Pharmaceutical Society, England, UK and currently pursuing his overseas pharmacy assessment programme (MSc) at Aston University, UK. He had his MPhil degree in Pharmaceutical Chemistry at Kwame Nkrumah University of Science and Technology. He has about 5 years’ experience as a community Pharmacist and has also taught in academic institutions like KNUST, Kumasi Technical University, Royal Ann College of Health, and G-Health Consult. He likes to spend time reading medical research articles and loves sharing his knowledge with others.
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