Wednesday, 17 November 2010

MRCP revision battle 52.3: Metformin

Metformin's mechanism of action is:
  • increasing gluconeogenesis
  • increasing insulin sensitivity and therefore increasing peripheral utilisation of glucose
  • possibly by decreasing GI absorption of carbohydrates

Metformin works only in the presence of endogenous insulin and is therefore only effective if there is residual functioning pancreatic islet cells.

Adverse effects of metformin include:
  • GI upset - to an intolerable degree in up to 20% of subjects
  • decreased B12 absorption - rarely clinically relevant but popular in MRCP questions
  • rarely it may provoke lactic acidosis - usually only if there is also renal impairment.

Contra-indications to metformin include:
  • eGFR <30 
  • IV contrast
  • stop of morning of general anaesthesia
  • pregnancy
  • breast feeding

Now on to a cardiac drug as we enter the cardiology section of today's battles...