How metformin works
Metformin is a blood sugar-lowering drug. Its exact action, as well as the side effects of metformin, result from a variety of effects that the drug exerts in the body:
After a carbohydrate-rich meal, the pancreas secretes the hormone insulin to keep blood glucose levels within the normal range. The sugars contained in food are digested in the intestine and absorbed into the blood in the form of the basic unit glucose.
The glucose circulating in the blood reaches the target cells through the insulin secreted, where it is available for energy production. The liver and muscles can also store excess glucose and release it back into the blood as needed. In addition, the liver can also form glucose from other nutrients such as fats and amino acids (building blocks of proteins).
Additional effects of metformin: It delays glucose uptake in the intestine, so that blood glucose levels rise less after meals (postprandial blood glucose level), and increases insulin sensitivity (i.e. metformin ensures that target cells respond more strongly to insulin, which improves glucose uptake into the cells).
Metformin also has a beneficial effect on fat metabolism, which is why it is preferred in overweight patients.
Absorption and degradation
After oral administration (as a tablet or drinking solution), about half to two-thirds of the active ingredient is absorbed into the blood. Metformin is not metabolized in the body. About 6.5 hours after ingestion, half of the active ingredient is excreted by the kidneys.
Uniformly high levels of active ingredient in the body set in after one to two days if taken regularly.
When is metformin used?
Outside the approved indications (i.e., “off-label”), the active ingredient is also used in cases of pre-diabetes and, in some cases, gestational diabetes.
Normally, metformin is taken for a longer period of time to positively influence the metabolic situation.
Metformin & childbearing in polycystic ovary syndrome
Polycystic ovary syndrome (PCO) is a hormonal disorder in women that can lead to infertility, among other things. Some studies and individual therapy trials showed that metformin can help.
Metformin can improve the insulin resistance and abnormally increased testosterone production often present in PCO, enabling patients to become pregnant.
The use of metformin after pregnancy varies greatly from individual to individual and is decided on a case-by-case basis by the treating physician.
How metformin is used
Typically, 500 to 850 milligrams of metformin are taken two to three times daily with or after meals. After 10 to 15 days, the attending physician assesses the effect of the treatment on blood glucose levels and, if necessary, increases the dose. The metformin dose can be increased to a maximum of 1000 milligrams three times a day – corresponding to a daily dose of 3000 milligrams.
In cases of insufficient blood glucose reduction, very high blood glucose levels at the beginning of therapy or concomitant diseases (e.g. diseases of the cardiovascular system or kidneys), metformin is combined with other active ingredients:
In Germany, Austria, and Switzerland, combination preparations of metformin are available with the following other blood glucose-lowering agents: pioglitazone, various gliptins (inhibitors of the enzyme DPP4), and gliflozins (inhibitors of a specific sodium-glucose transporter in the kidney).
Combination with insulin may also be considered.
Side effects from metformin usually occur at the beginning of therapy and improve significantly after a few days to weeks.
Very often (in more than one in ten patients), symptoms of the digestive tract occur, such as nausea, vomiting, diarrhea, and abdominal pain. These side effects may improve if metformin is taken with meals. The digestive tract then becomes less irritated.
Frequently (in one in ten to one in a hundred patients), changes in taste occur (especially a metallic taste). These have no clinical value, but can be very disturbing.
Very rarely (in less than one in ten thousand patients), the side effect lactic acidosis develops. This involves acidification of the body by lactic acid, which has been observed mostly in patients with kidney disease. Signs of metformin lactic acidosis include muscle pain, malaise, abdominal pain, labored breathing, and low body temperature.
What should be considered when taking metformin?
Contraindications
Taking metformin is contraindicated in:
- hypersensitivity to the active substance
- @ lactic acidosis
- severe hepatic and renal impairment
Two days before to two days after surgery and for X-ray examinations involving intravenous contrast administration should be paused with the use of metformin.
Drug Interactions
It is not recommended to take metformin concomitantly with the following medications:
- Medications that affect blood glucose such as glucocorticoids (“cortisone”) and circulatory stimulants (sympathomimetics)
- @ certain diuretic medications (especially loop diuretics)
Experts also recommend avoiding alcohol during therapy with metformin.
Age restriction
Metformin is approved for use in children and adolescents over the age of ten, in combination with insulin if necessary.
Pregnancy and lactation
Breastfeeding is allowed without restriction while taking metformin.
How to obtain medication with metformin
In Germany, Austria and Switzerland, preparations containing metformin are available only on prescription in any dosage and can only be obtained from pharmacies.
How long has metformin been known?
The class of biguanides to which metformin belongs was chemically modeled on a natural substance found in honeysuckle (Galega officinalis), which has long been used in folk medicine.
In 1929, it was first discovered that metformin could effectively lower blood glucose levels. However, after it was possible at about the same time to extract insulin, with which blood sugar can be influenced even more effectively, metformin was not investigated further.
