Metformin, sold under the brand name Glucophage, among others, is the main first-line medication for the treatment of type 2 diabetes, particularly in people who are overweight. It is also used in the treatment of polycystic ovary syndrome. It is not associated with weight gain and is taken by mouth. It is sometimes used as an off-label adjunct to lessen the risk of metabolic syndrome in people who take antipsychotics.Metformin is generally well tolerated. Common adverse effects include diarrhea, nausea, and abdominal pain. It has a small risk of causing low blood sugar. High blood lactic acid level is a concern if the medication is used in overly large doses or prescribed in people with severe kidney problems. It is not recommended in those with significant liver disease. Metformin is a biguanide antihyperglycemic agent. It works by decreasing glucose production in the liver, by increasing the insulin sensitivity of body tissues, and by increasing GDF15 secretion, which reduces appetite and caloric intake.Metformin was discovered in 1922. French physician Jean Sterne began the study in humans in the 1950s. It was introduced as a medication in France in 1957 and the United States in 1995. It is on the World Health Organizations List of Essential Medicines. Metformin is the most widely used medication for diabetes taken by mouth. It is available as a generic medication. In 2020, it was the third most-commonly prescribed medication in the United States, with more than 92 million prescriptions.
G. officinalis itself does not contain any of these medications, but isoamylene guanidine; phenformin, buformin, and metformin are chemically synthesized compounds composed of two guanidine molecules, and are more lipophilic than the plant-derived parent compound.Metformin was first described in the scientific literature in 1922, by Emil Werner and James Bell, as a product in the synthesis of N,N-dimethylguanidine. In 1929, Slotta and Tschesche discovered its sugar-lowering action in rabbits, finding it the most potent biguanide analog they studied. This result was completely forgotten, as other guanidine analogs such as the synthalins, took over and were themselves soon overshadowed by insulin.Interest in metformin resumed at the end of the 1940s. In 1950, metformin, unlike some other similar compounds, was found not to decrease blood pressure and heart rate in animals. That year, Filipino physician Eusebio Y. Garcia used metformin (he named it Fluamine) to treat influenza; he noted the medication "lowered the blood sugar to minimum physiological limit" and was not toxic. Garcia believed metformin to have bacteriostatic, antiviral, antimalarial, antipyretic, and analgesic actions. In a series of articles in 1954, Polish pharmacologist Janusz Supniewski was unable to confirm most of these effects, including lowered blood sugar. Instead he observed antiviral effects in humans.French diabetologist Jean Sterne studied the antihyperglycemic properties of galegine, an alkaloid isolated from G. officinalis, which is related in structure to metformin, and had seen brief use as an antidiabetic before the synthalins were developed.