Biguanides (Formulary)

TAM (Treatments and Medicines) NHS Highland
NHS Highland

Use of metformin in surgery, investigations with contrast media and conditions predisposing to tissue hypoxia

Surgical procedures Stop 24 hours beforehand.
Withhold for at least 48 hours.
Investigations with contrast media Discontinue on day of examination.
Restart 48 hours later. If eGFR less than 60 mL/min/m2 then check renal function before restarting.
Myocardial infarction Withhold at time of infarct.
Consider restarting 5 days post-infarct.
Acute coronary syndrome Withhold during ischaemic pain.
Restart when pain free for 48 hours.
Acute limb ischaemia Withhold until acute event resolved.
Sepsis Withhold until acute event resolved.
Respiratory failure Withhold until acute event resolved.
Acute kidney injury Only restart metformin when the eGFR is greater than 30mL/min and back to patient’s normal baseline.

 

METFORMIN - (First line)

Therapy notes

MHRA advice: Metformin and reduced vitamin B12 levels: new advice for monitoring patients at risk (June 2022) (www.gov.uk).

MHRA advice: Metformin in pregnancy: study shows no safety concerns (March 2022) (www.gov.uk).

For use in type 2 diabetes, refer to guidance.  Tablets are first choice and modified release tablets are second choice.

  • Advise patients to stop metformin during vomiting or diarrhoeal illnesses
  • The modified release tablets are restricted to use in patients intolerant of immediate-release metformin and in whom the m/r tablet allows the use of a dose of metformin not previously tolerated or in patients for whom a once-daily preparation offers a clinically significant benefit.  

Formulation and dosage details

Formulation:

Tablets 500mg

Dosage:

Tablets: initially 500mg with breakfast for 1 week then 500mg with breakfast and evening meal for 1 week then titrated as required; maximum 2 grams daily in divided doses.

Formulation and dosage details

Formulation:

Modified release tablets 500mg, 750mg, 1gram

Dosage:

Modified release tablets: patients who have been taking the immediate-release metformin may start with the same daily dose of metformin modified release tablets and titrate up to a maximum of 2 grams daily.

Editorial Information

Document Id: F173