Urea: Effect, Uses & Risks

Urea, also called urea, is an end product of protein metabolism in the body and is excreted in the urine. Its formation occurs in the so-called urea cycle via ammonia synthesis from amino acids. Urea concentration in urine, along with creatinine concentration, is an indicator of various disorders of protein metabolism and kidney disease.

What is urea?

Urea, also known as urea, is an end product of protein metabolism in the body and is excreted in the urine. Urea is the first organic compound to have been synthesized from inorganic starting materials. With the synthesis of urea from potassium cyanate and ammonia, the German chemist Friedrich Wöhler proved in 1828 that no organisms were needed in the production of organic substances. Thus, the mysterious boundary between organic and inorganic chemistry disappeared. The chemical name for urea is carbonic acid diamide. It contains two amino groups and a CO double bond in the molecule. The molecular formula of urea is CH4N2O. Urea is a non-toxic, white and crystalline substance with hygroscopic (water attracting) properties, which is most important as a fertilizer in agriculture. Along with carbon dioxide, water and minerals, it is also one of the most important metabolic end products of the body.

Pharmacological action

The organism produces urea through the so-called urea cycle. Ultimately, the amino and carboxyl groups of amino acids are used to synthesize urea via this cycle. The nitrogen-free compound that remains is further degraded to carbon dioxide and water or recycled back into the metabolism. The amino groups can also be reintegrated into the metabolic cycle. In the form of urea, the nitrogen is no longer available for building up the body’s own substances and is therefore excreted. The nitrogen balance can only be maintained by protein-containing foods. Although the urea concentration in the urine can fluctuate greatly depending on nutritional status and physical situation, without being able to make a statement about the state of health, a long-term over- or under-concentration indicates health disorders. Excessive urea concentrations can occur with increased protein breakdown due to catabolic diseases, such as cancer, intense inflammatory processes, or necrosis. Filtration disorders of the kidneys also lead to elevated urea levels because the ammonia produced by metabolism is no longer properly returned to the metabolic cycle. The only alternative then is to convert it into urea. Otherwise, the increased ammonia level would lead to poisoning of the body. Urea levels that are too low indicate a diet that is very low in protein or diseases with absorption disorders, such as celiac disease. However, urea analysis can only lead to a meaningful diagnosis in conjunction with other laboratory values.

Medical application and use

Medically, urea is important both analytically and therapeutically. The analytical importance results from the indicator function for various diseases mentioned earlier. Urea does not play a function in the eventual treatment of internal diseases. Instead, it has properties that make it interesting for use in cosmetics, for example. For example, urea is hygroscopic, i.e. it attracts water. It is contained in sweat to make the skin supple. If urea is missing, the skin becomes dry and tends to develop eczema and itching. Therefore, urea is contained in many creams to provide the skin with adequate moisture. Generally, there are 2 to 20 percent urea in urea creams. Another possible application for urea comes from its keratolytic (callus-dissolving) effect. Formulations containing 40 percent urea are able to dissolve corns and calluses. Furthermore, creams containing urea are used in the treatment of neurodermatitis and psoriasis. A particularly interesting field of application is the use for nail fungus, whereby the nail is softened in order to remove the fungus in this way.

Risks and side effects

Creams containing urea should not be used if the skin is hypersensitive to urea. This also applies to inflamed and injured skin. Eye and mucous membrane contact with urea-containing agents should also be avoided. Experience with the treatment of children is not available.Therefore, the use of urea-containing substances is also not recommended here. Hypersensitivity reactions are rare. However, should they occur, burning, itching or reddening of the skin may occur. Sometimes urea increases the release of drugs from other creams and ointments, increasing its effect.