Notes for: BiguanidesLast edited [13/07/2012 09:25:05]
1. Metformin is particularly advantageous as first line therapy in all overweight patients. However metformin should not be restricted solely to overweight patients - it may be used with a sulphonylurea in patients who are not grossly overweight.
2. Metformin MR should only be used where the standard-release tablets have been tried and are not tolerated due to GI problems. Any new prescription of the MR preparation should be reviewed soon after initiation and discontinued if not tolerated or ineffective.
3. Local advice: In some circumstances Metformin may cause a lactic acidosis, which may be profound and life threatening. This is a rare complication and almost exclusively occurs in association with renal impairment. Nonetheless, many patients can safely tolerate metformin with renal impairment; the precipitating factor for lactic acidosis usually being an intercurrent medical complication such as infection or dehydration. The question is therefore at what stage the metformin should be stopped. Metformin should not routinely be used in patients with stage 4 or 5 CKD (eGFR < 30 mL / min). In stable uncomplicated CKD stage 3, metformin can continue to be used with appropriate education (see below) and at lowest possible dose. In complicated stage 3 CKD (presence of otherwise unexplained anaemia and/or biochemical abnormality of calcium, phosphate or bicarbonate), use of metformin should be discussed as part of the renal advice/guidance/referral process (as per CKD guidelines), and if continued use at low dose. In stage 3 CKD with declining eGFR (> 5 mL / min / year), metformin should be electively discontinued before patients reach CKD stage 4. Unstable patients with fluid balance issues, recurrent infections, heart failure etc should have their metformin stopped at an earlier stage (eGFR 45 mL / min would be an appropriate threshold). Stable patients with diabetes with CKD stage 3 who are taking metformin should be educated with regard to management during significant intercurrent infection, or other medical complications, particularly those which give rise to dehydration. In particular, patients treated with metformin and coexisting treatments with ACE inhibitors or sartans should be advised to temporarily withhold all of these drugs when affected by vomiting, diarrhoea, etc, since in these circumstances a transient reduction in GFR can be realistically anticipated. The patient’s usual medication can be restarted once their hydration status is corrected and renal function has been checked. Alternatives to metformin include sulphonylureas (also to be used with caution in patients with chronic kidney disease due to risk of hypoglycaemia - use in low dose and avoid long acting preparations), pioglitazone (noting risk of worsening cardiac failure/oedema) and of course insulin.
4. NICE Public health guidance (July 2012) Preventing type 2 diabetes: risk identification and interventions for individuals at high risk
5. Metformin is also used in polycystic ovary syndrome (unlicensed indication).
Last edited [13/07/2012 09:25:29]