What are the contraindications for the administration of metformin

Metformin is strongly contraindicated in situations that can constitute a background for the appearance of lactic acidosis (see below for more details). The medicine is also contraindicated in patients with impaired renal function (serum creatinine > 1.5 mg/dl [132.6 mmol/L] in men or > 1.4 mg/dl [123.8 mmol/L] in women). In elderly patients, the decision whether to administer metformin is based on the creatinine clearance (metformin should not be prescribed if this is < 60 ml/min/1.73 m2). The renal function should be evaluated every year. In patients who need contrast media intravenously for radiologic examinations, metformin should be discontinued 1-2 days before and after the examination. Apart from these situations, the administration of metformin is also contraindicated in:

• acute or chronic cardiac insufficiency

• respiratory insufficiency

• septicaemia

• significant hepatic insufficiency

alcohol abuse

• history of lactic acidosis

• pregnancy and lactation

• conditions of shock

• serious illness and surgical interventions (anaesthesia): temporary discontinuation

In the patient under discussion, the frequent consumption of beer concerns the treating physician.

After the gradual increase of the dose (two 850 mg tablets daily), the patient comes back complaining of epigastric pains, manifested around half-an-hour after the intake of the metformin tablet. Are epigastric pains a side effect of metformin?

The undesirable side effects of metformin emanate mainly from the peptic system. It can cause epigastric pains, nausea, anorexia, metallic taste in the mouth, flatulence and diarrhoea. Some patients complain of a feeling of easy fatiguability. The undesirable side effects are more frequent at the beginning of the treatment (some authors report rates of 30 percent) but they often subside after a few days or after a transient decrease of the dose. It is reported that 5-10 percent of the patients receiving metformin are forced to interrupt it because of its undesirable side effects (mainly due to diarrhoea).

The epigastric pain in this particular patient may also be due to the aspirin or statin that he receives. Also, smoking causes gastritis.

Another side effect of metformin also reported is a decrease of vitamin B12 levels in the blood of the patients, although this does not yet have a proven clinical significance.

The worst undesirable side effect of metformin - albeit rare - is lactic acidosis which is manifested in patients that receive metformin despite contraindications. The mechanism of lactic acidosis in those receiving the medicine is not absolutely elucidated. Biguanides are bound to the mitochondrial membranes and inhibit the aerobic metabolism. Secondarily, an increase of the anaerobic metabolism is caused, and consequently lactic acid production increases. Although the incidence of lactic acidosis with metformin is around 0.03 cases per 1000 patient-years of treatment, the mortality rate is high, roughly 50 percent. Lactic acidosis can also happen in diabetics who do not receive metformin, and also in patients who deliberately consume excessively big doses of the medicine without contraindications.

After two years of good control with metformin, the current patient had not managed to stop smoking and the lipid profile still remained abnormal. He visits the Diabetes Clinic looking obviously weak and reports recent hospitalization in a cardiologic unit because of an acute myocardial infarction. He now uses treatment with insulin. Can the patient once again begin metformin?

Metformin is contraindicated, as was mentioned before, in every situation of hypoxia, such as chronic congestive heart failure, which causes an increase in lactic acid production. The recent development of myocardial infarction, unless it is accompanied by cardiac insufficiency with haemodynamic instability, is no longer considered to be a contraindication for the administration of metformin. Previous guidelines definitely excluded these patients for the six months following the infarction.

The patient wonders why his sister, who does not have DM, also receives metformin from her doctor. What are the indications for metformin administration other than for Type 2 DM?

Metformin is also prescribed for women for conditions often associated with polycystic ovary syndrome (which is frequently accompanied by insulin resistance). These include oligomenorrhoea, infertility because of anovulation, hirsutism, obesity and DM. There are small studies that refer to the prevention of gestational DM in women with polycystic ovary syndrome, but no double blind study.

The administration of metformin is contraindicated during pregnancy.

Metformin is allowed in adolescents and children with Type 2 DM.

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  • donna
    Can metformin cause epigastric pain?
    8 years ago

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