Biguanide

French physician Jean Sterne published the first clinical trial in 1957 suggesting metformin as a treatment for diabetes. The United Kingdom introduced this drug in 1958 followed by Canada in 1972, and the United States in 1995. As of 2010, metformin was one of only two oral antidiabetics in the World Health Organization model list of essential medicines, the other being glibenclamide. Metformin is believed to enjoy the popularity of being the most widely prescribed antidiabetic drug in the world. It has been estimated that the United States alone has filled nearly a million prescriptions in 2010 for its generic formulations. Biguanides are not hypoglycemic agents; rather they promote euglycemia (antihyperglycemic). Biguanides are used both as monotherapy and in combination with other oral hypoglycemic agents to control hyperglycemia. Although very safe in most instances, the major toxicity from acute or chronic use of biguanides has been reported to be lactic acidosis. In fact, the high rate of severe lactic acidosis was the only major cause of withdrawal of phenformin from the US market in 1976.

Biguanide [56-03-1], C2H7N5, Mr 101.11, mp 130 ℃ (which decomposes violently at 142 ℃), is a moderately strong base (pKb 2.9). It is readily soluble in water and ethanol, and insoluble in ether, benzene, and chloroform. The free base decomposes gradually in aqueous solution. Biguanide forms stable salts with most acids.

Biguanides are used as an oral drug for the management of mild to moderately severe noninsulin-dependent diabetes mellitus, or NIDDM, (Type II) in obese or overweight patients who are usually above 40 years of age. It is important that for the administration of this drug the disease should have adult onset. Polymeric biguanides were originally developed as a presurgery antimicrobial scrub and in 1977, it was introduced in the market for treating pools and spas as a disinfectant under the trade name Baquacil. The US Environmental Protection Agency approved this agent as the only nonhalogen sanitizer of pools and spas. Biguanide itself is combined with algaecides and hydrogen peroxide for periodic oxidation of pools and spas. Biguanides are incompatible with chlorine, ozone, detergents, and ionizers, but are compatible with water ion balancing chemicals. Biguanide in the form of polyaminopropyl biguanide serves as a disinfectant, and preservative for skin disinfection, contact lens cleaning solutions, and deodorant body sprays. Biguanides reduce the surface tension of water, which gives it a smoother feeling. They are stable in sunlight and temperature. At recommended concentrations when used in pools and spas, biguanides do not irritate the skin or eyes and do not corrode the pool equipment.

Globally, hundreds of millions of patients are prescribed this drug annually. Metformin was discovered before the era of target-based drug discovery, and its molecular mechanism of action remains an important focus of diabetes research. Advances in our understanding of metformin’s molecular targets are likely to enable target-based identification of secondgeneration drugs with similar properties, a development that has been a difficult task until now. Besides its potent antidiabetic properties, Metformin’s potential as a targeted anticancer agent is being explored in a number of laboratories throughout the world.

Crystallise biguanide from EtOH. It gives a red Cu derivative, and it forms salts with many metals. The monohydrochloride has m 235o [38664-03-8] and the dihydrochloride forms plates with m 248o (213-214o, also reported) [25836-74-2]. [Beilstein 3 H 93, 3 I 44, 3 II 76, 3 III 171, 3 IV 162.]