Metformin -Antidiabetic drugs

Antidiabetic drugs
Antidiabetic drugs are medications that work to lower blood glucose concentrations, or the amount of sugar in the blood. They are an important way of treating  gestational,  type 1 and  type 2 diabetes mellitus.
 There are many types of antidiabetic drugs. Herbal remedies and other forms of alternative medicine are also used for diabetes treatment, especially in areas where modern drugs are not easily available.Antidiabetic drugs exert their useful effects through: (1) increasing insulin levels in the body or (2) increasing the body's sensitivity (or decreasing its resistance) to insulin, or (3) decreasing glucose absorption in the intestines.
 Antidiabetic Drugs That Increase Insulin
Metformin
Metformin is one of the oldest, most widely used, and least-expensive antidiabetic drugs for treatment of type 2 diabetes (T2DM). It is one of several orally-available medicines for this disease, but is very different structurally from the other compounds.  

brand name

Glucophage 
Chemical structure of metformin 

uses
Metformin is used to help control blood glucose levels in persons with type 2 diabetes by reducing glucose production in the liver and increasing sensitivity to existing insulin. It is not a replacement for injected insulin and is not used in treating type 1 diabetes. It is often used in combination with other medications as part of regimen that includes recommendations for weight loss and decreased caloric intake.Metformin is also used in treating polycystic ovary syndrome
dosage
Metformin is provided as tablets to take by mouth; the tablets may contain metformin as the only active ingredient or may also contain other medicines. The regular tablet is usually taken with meals two or three times a day. The extended-release tablet is usually taken once daily with the evening meal. Tablets are usually taken at the same time each day and should be swallowed whole. The dose of metformin is adjusted gradually in response to how well it is tolerated and how well the patient's blood sugar levels respond to the drug.
mechanism of action
In contrast to some other medications, the precise (molecular) mechanism of metformin is not known. However, it is well-established that metformin acts as an insulin sensitizer in that it increases the blood glucose-lowering activity of insulin. The beneficial glycemic effects of metformin are mainly attributed to lowering the amount of glucose produced by the liver (hepatic gluconeogenesis), and increased peripheral tissue insulin sensitivity. Metformin probably works by interrupting mitochondrial oxidation in the liver and by correcting intracellular calcium abnormalities in tissues such as the liver, fat, and skeletal muscle.[2]
Metformin is excreted unchanged in the urine. The body does not seem to modify metformin, as no metabolites have been identified in humans, and the drug is not excreted in the bile. After oral administration, about 90% of the absorbed drug is eliminated via the kidneys in the first 24 hours, with a plasma elimination half-life of approximately 6.2 hours. In blood, the elimination half-life is approximately 17.6 hours, suggesting that the drug may enter and leave red blood cells.
Benefits
Blood glucose control; tendency to lose weight; improved lipid levels...
Side Effects
Metformin alone does not lead to low blood sugar levels; however, it is often taken in combination with other medications that can cause this. Symptoms of low blood sugar (hypoglycemia) include shakiness, dizziness or lightheadedness, sweating, nervousness or irritability, sudden changes in behavior or mood, headache, numbness or tingling around the mouth, weakness, pale skin, hunger, and clumsy or jerky movements.Metformin itself may cause may cause side effects. In most patients, the effects are not troublesome enough to mandate discontinuation. Commonly-reported side effects of metformin include: diarrhea, bloating, stomach pain, gas, constipation, unpleasant metallic taste in mouth, heartburn, headache, sneezing, cough, runny nose, flushing of the skin, nail changes, and muscle pain.Chest pain or rash are serious side effects that require immediate discontinuation of metformin and medical evaluation.
Risks and Precautions
Metformin carries a very small risk of causing lactic acidosis; the risk is about 0.03 cases/1000 patient-years, with approximately 0.015 fatal cases/1000 patient-years. Lactic acidosis is characterized by elevated blood lactate levels (>5 mmol/L), decreased blood pH, and electrolyte disturbances. When metformin is implicated as the cause of lactic acidosis, metformin plasma levels >5 µg/mL are generally found.[3]