What are Biguanides?

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  • Written By: Helga George
  • Edited By: Michelle Arevalo
  • Last Modified Date: 19 October 2019
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Biguanides are a class of chemicals that include some important pharmaceutical drugs. Metformin, thought to be the most-prescribed anti-diabetic drug, is in this class. There is also a drug for treating malaria called proguanil that is a biguanide. This class of compounds was originally derived from the French lilac plant.

Diabetes mellitus is a syndrome of diseases that involves an excess of glucose in the blood. Extremely high levels can cause coma and be lethal. Type 1 diabetes is an autoimmune condition. In it, the patient’s pancreas produces insufficient insulin, and this shortage must then be overcome either by injections or an automatic pump. With Type 2 diabetes, the cells have lost the ability to respond to insulin.

Type 2 diabetes is often correlated with obesity. Lifestyle changes, such as increased exercise, diet modification, and weight loss, can sometimes control this disease. Gestational diabetes can occur during pregnancy. Prediabetes is a condition in which a person has elevated blood sugar and is at risk of developing Type 2 diabetes.

Paradoxically, blood sugar levels that are too low can also be very dangerous and lead to coma and death. This condition is called hypoglycemia. This is a particular problem for people who take insulin to control diabetes, but it is also a side effect of many anti-diabetic drugs.


In the past, several types of biguanides were used to treat diabetes, however all but one of the drugs were found to be too toxic for use. Over time the drug metformin has become the drug of choice to treat people with Type 2 diabetes. Unlike other anti-diabetic drugs, which can cause weight gain, this drug does not have that side effect. It can cause weight loss and reduces the level of fats and cholesterol in the bloodstream. This drug does not cause hypoglycemia.

Metformin has been shown to cause a decrease in mortality from diabetes, primarily by reducing heart disease and strokes. The exact mechanism of action is unclear. The primary action of biguanides is to reduce the liver’s production of glucose, which affects the levels of fasting glucose in the morning. These compounds also increase the intake of glucose by muscle cells, thus lowering the levels in the blood.

Another effect is to reduce the degree of insulin resistance by the body. Thus, diabetics who take insulin can lower their levels of insulin treatment. This even applies to Type 1 diabetics. Metformin is frequently combined with other anti-diabetic drugs, such as sulfonylureas.

Prediabetes treatment is another function of metformin. This compound is also sometimes used to treat polycystic ovary syndrome. It is used for this purpose because this disease is associated with increased insulin resistance. When treating this disorder, metformin can cause irregular menstrual periods and increase the chance of pregnancy.

For most people, the side effects of metformin are minor, especially compared to the other biguanides. They primarily consist of digestive upset, which generally decreases after a patient has been on the drug for a few weeks. A more serious side effect is lactic acidosis, which occurs rarely and is primarily seen with older people who have kidney disease, congestive heart failure, or lung disease. Such people should not take metformin.

In addition to treating diabetes, another biguanide is used as one of the anti-malarial drugs. Proguanil is taken ahead of time by travelers to prevent getting the disease. Generally, this drug is taken with another medication that is effective against malaria.

One biguanide compound is used as disinfectant. Polyaminopropyl biguanide (PAPB) has an array of uses as an anti-microbial agent. These range from use in contact lens solutions to use in swimming pools as an alternative to chlorine. It is considered to be non-irritating to the skin or eyes.


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