Pharmacy Diabetes

B-2.1 Biguanides_Metformin-overview

Biguanides are a class of diabetes medications used in type 2 diabetes. Biguanides work by preventing the production of glucose in the liver, improving the body’s sensitivity towards insulin, and reducing the amount of glucose absorbed by the intestines.
Biguanides are insulin sensitizers and do not cause hypoglycaemia as a side effect. They are one of the few diabetes medicines that will continue to be prescribed once insulin is initiated to keep the prescribed dose of insulin as low as practicable.
Metformin is the only biguanide registered for use for Australia.
  • Immediate Release: (IR) prescribed up to three times a day
  • Modified Release: (MR) or sustained release (SR) prescribed once or twice daily.
Mode of Action
  • Lower blood glucose levels mainly by reducing gluconeogenesis (the production of glucose from non-carbohydrate carbon substrates) in the liver and as a result reduces the level of glucose in the blood.
  • Reduce insulin resistance enabling the body to absorb glucose in the blood. 
  • Do not stimulate the production of more insulin and so do not cause hypoglycaemia as a side effect.
  • All doses should be taken with food and never on an empty stomach. Biguanides are known for causing gastrointestinal side effects including nausea, bloating and diarrhoea. Sometimes they can also cause constipation.
  • Known for causing intermittent diarrhoea. People may put this symptom down to something they have eaten especially when eating out and there is limited control over food intake (i.e., at a friend’s house for a meal).